Compositions and methods for treatment of Toxoplasma gondii and other apicomplexans

ABSTRACT

Pyrimidine auxotroph mutants of apicomplexans are provided which are mutated in one of six enzymes of the de novo pyrimidine biosynthesis pathway. Also provided are methods of protecting an animal against infection by apicomplexans by administering a pyrimidine auxotroph mutant and methods for screening for inhibitors of pyrimidine salvage enzymes in apicomplexans.

INTRODUCTION

[0001] This application is a continuation-in-part of PCT/US01/03906, filed Feb. 7, 2001, which claims the benefit of priority of U.S. Provisional Application No. 60/180,604, filed Feb. 7, 2000, now abandoned.

[0002] This invention was supported in part by funds from the U.S. government (NIH Grant No. R01 AI41930) and the U.S. government may therefore have certain rights in the invention.

BACKGROUND OF THE INVENTION

[0003]Toxoplasma gondii is an obligate intracellular parasite which can infect many warm-blooded vertebrates including both mammals and birds. In humans, it has been recognized as a major cause of severe congenital disease and a common cause of infection in immunocompromised hosts. Recently, the parasite has received increased attention as an important opportunistic pathogen affecting up to 25% of AIDS patients (Kasper, L. H. (1994) Toxoplasma infection and toxoplasmosis. Harrison's textbook of Internal Medicine Ed. EiCE Braunwald, NY, McGraw-Hill, 13th edition 903-908). Improved chemotherapy for T. gondii is urgently needed to treat infected immunocompromised subjects.

[0004] The subclass Coccidiasina includes the order Hemosporidia, which contains the genus Plasmodium (causative agent of malaria). Coccidiasina also includes the order Eucoccidiorida which includes the suborder Eimeriorina. T. gondii belongs to the order Eucoccidiorida and to the suborder Eimeriorina. Within this latter order genera such Toxoplasma, Sarcocystis, Neospora, Eimeria, Cryptosporidium, Besnoitia and Hammondia are included.

[0005]T. gondii is relatively easy to handle and maintain. Consequently this parasite has become an important model for the study of how obligate intracellular parasites in the subclass Coccidiasina function.

[0006] It is known that mammals can be immunized against toxoplasmosis. However, all parasite strains and mutants so far developed as potential vaccines for toxoplasmosis share one common and serious flaw. Specifically, the T. gondii vaccines described thus far invariably kill immunocompromised animals, even with only administration of small parasite doses (Pfefferkorn, E. R. and L. C. Pfefferkorn. 1976. Exp. Parisitol. 39:365; Radke, J. R. amd M. W. White. 1999. Immunity 67:5292).

[0007] The present invention relates to a method for chemotherapy via creation of attenuated pyrimidine auxotroph mutants of obligate intracellular parasites of the phylum apicomplexa. A vaccine has now been developed for immunizing animals of various types against T. gondii. This vaccine makes use of a specific pyrimidine auxotroph mutant of T. gondii which has been found to give immunity without apparent concomitant chronic infection of the animal. It is believed that pyrimidine auxotrophic mutants can also be used to immunize animals against other apicomplexans.

SUMMARY OF THE INVENTION

[0008] An object of the present invention is to provide nucleic acid sequences encoding carbamoyl phosphate synthase (CPSII) of T. gondii.

[0009] Another object of the present invention is to provide a pyrimidine auxotroph mutant of T. gondii which can be used as a vaccine against T. gondii infection. This live-attenuated pyrimidine auxotroph mutant of T. gondii described herein does not kill immunocompromised animals even when administered in high doses.

[0010] Another object of the present invention is to provide a method for protecting an animal against infection by T. gondii which comprises administering to an animal a pyrimidine auxotroph mutant of T. gondii which is mutated in one of the six enzymes of the de novo pyrimidine biosynthesis pathway.

[0011] Yet another object of the present invention is to provide pyrimidine auxotroph mutants of other apicomplexans and methods of using these mutants to protect against infection from other apicomplexans, wherein the mutants are mutated in one of the six enzymes of the de novo pyrimidine biosynthesis pathway.

[0012] The pyrimidine auxotroph mutants of the present invention can also be used to screen for novel inhibitors of pyrimidine salvage enzymes in T. gondii and other apicomplexans.

[0013] Another object of the present invention is a vaccine for protection against infection by an apicomplexan which comprises the pyrimidine auxotroph mutant of the present invention and a pharmaceutically acceptable carrier or diluent.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 shows the genomic DNA (SEQ ID NO:1) and cDNA (SEQ ID NO:2) derived clones obtained from the cpsII locus of T. gondii. Genomic DNA clones and their names are shown in

boxes, cDNA clones are shown in

boxes. The complete T. gondii CPSII cDNA is encoded on 37 exons spanning about 24 kb of the genomic DNA.

DETAILED DESCRIPTION OF THE INVENTION

[0015]T. gondii has a complete pathway for the de novo biosynthesis of pyrimidines (Schwartzmann J. D. and Pfefferkorn, E. R. J. Parasitol. 1981 67:150-158; Asai et al. Mol. Biochem. Parasitol. 1983 7:89-100). UMP, the first major end-product of the pathway, is synthesized from bicarbonate, glutamine, ATP, aspartate, and phosphoribosyl pyrophosphate (P-rib-PP) is catalyzed by six major enzymes: carbamoyl phosphate synthase (CPS), aspartate transcarbamylase (ATC), dihydroorotase (DHO), dihydroorotase dehydrogenase (DHOD), orotate phosphoribosyl transferase (OPT), and orotidylate decarboxylase (ODC or URA3). The pathway begins with CPS which combines glutamine, ATP and bicarbonate to form carbamoyl phosphate. The glutamine-specific CPS activity involved in de novo pyrimidine biosynthesis is referred to as CPSII and the enzyme is typically localized in the nucleolus of eukaryotic cells (Davis, R. H. Microbiol. Reviews. 1986 50:280-313). ATC then combines carbamoyl phosphate and aspartate to form carbamoyl aspartate. The third reaction, catalyzed by DHO, yields dihydroorotate. DHOD then oxidizes dihydroorotate to orotate with the reduction of NAD. OPT then phosphoribosylates orotate to OMP. The sixth step, catalyzed by OMP Decarboxylase (URA3), converts OMP to UMP. UMP is the precursor of all pyrimidine nucleotides and deoxyribonucleotides.

[0016] In the Urea Cycle of ureotelic animals, carbamoyl phosphate is combined with ornithine, derived from ammonia, to form citrulline during de novo arginine biosynthesis. The CPS involved in arginine biosynthesis is referred to as CPSI. In some eukaryotes such as yeast, where CPSI is cytosolic, mutants of CPSII are a bit leaky because of some “mixing” of these two pools of carbamoyl phosphate. In many eukaryotes, CPSI is confined to the mitochondrial matrix and carbamoyl phosphate produced from CPSI in the Urea Cycle is unavailable to the carbamoyl phosphate “pool” which feeds into de novo pyrimidine biosynthesis (Davis, R. H. Microbiol. Reviews. 1986 50:280-313). There is no mixing of CPSI and CPSII in T. gondii due to either sequestering of CPSI to a compartment such as the mitochondria or a lack of CPSI type activity in T. gondii. Thus, the CPSII involved in the de novo biosynthesis of pyrimidines is the first committed step of the de novo pathway of pyrimidine synthesis in T. gondii.

[0017] Comparative studies across many genera demonstrate extensive diversity in the de novo pathway's regulatory mechanisms, in the structure of its enzymes, and in the organization of the genes which encode the enzymes (Jones, M. E. Ann. Rev. Biochem. 1980 49:253-279). In many organisms, including man, the first three enzymes of de novo pyrimidine biosynthesis are found as multifunctional polypeptides. Typically, in higher eukaryotes the CPS, ATC, and DHO activities are encoded on a single gene, CAD, that specifies a single multifunctional polypeptide chain. In lower eukaryotes such as S. cerevisiae, the CAD-homologue gene specifies functional CPS and ATC domains, but a non-functional DHO domain. The organization of these CAD activities has evolved differently in various parasitic protozoa. In protozoan parasites of phylum Apicomplexa, including Babesia and Plasmodium species, the CPS activity is specified as an individual gene specifying a polypeptide with a single CPSII enzyme activity comprising the glutamine amido transferase (GAT) activity and the CPS activity; GAT+CPS=CPSH (Chansiri K. and Bagnara, A. S. Mol. Biochem. Parasitol. 1995 74:239243; Flores et al. Mol. Biochem. Parasitol. 1994 68: 315-318). This peculiar protozoan parasite gene organization is more similar to bacteria where CPS is monofunctional (Mergeay et al. Mol. Gen. Genet. 1974 133: 299-316.). T. gondii is also an Apicomplexan and it also specifies the CAD enzyme activities on individual polypeptides (Asai et al. Mol. Biochem. Parasitol. 1983 7:89-100). This difference in CAD gene organization between man and Apicomplexan parasites is reminiscent of the situation with DHFR and TS where these enzyme activities are present on a single polypeptide in Apicomplexan parasites (Bzik et al. Proc. Natl. Acad. Sci. USA 1987 84:8360-8364) and on individual polypeptides in man. The difference in DHFR-TS gene structure between parasites and man has provided significant opportunity for chemotherapy using compounds such as pyrimethamine.

[0018] The difference in the CAD gene structure for pyrimidine synthesis between parasites and man also provides a unique chemotherapeutic opportunity. Further, blocking the accumulation of UMP by attacking one of the de novo pyrimidine biosynthetic enzymes should have a more profound anti-parasite effect than, for example, blocking accumulation of dTMP via pyrimethamine and sulfonamide treatment which is the standard chemotherapy for recrudescent toxoplasmosis. The latter strategy primarily blocks tachyzoite DNA replication with little apparent effect on bradyzoites, whereas the former strategy is predicted to block both parasite RNA synthesis as well as DNA replication.

[0019] In addition to the novel protozoan gene organization of CAD, the CAD-encoded enzymes have unique properties and regulation that make them attractive targets for chemotherapy. The CPSII activity detected in T. gondii is primarily involved in de novo pyrimidine biosynthesis based on substrate preference (Asai et al. Mol. Biochem. Parasitol. 1983 7: 89-100). While the mammalian CPSI involved in the Urea Cycle is activated by N-acetyl glutamate, the CPSII activity found in T. gondii is not affected by this treatment. The T. gondii CPSII activity is inhibited by UTP, suggesting a pyrimidine-controlled regulatory circuit. While the CPSII activity of man is activated by P-rib-PP, the T. gondii CPS activity is not. In contrast to CPSII, other enzymes of the de novo biosynthetic pathway were broadly characterized to behave similarly to their higher eukaryotic counterpart. The T. gondii CPSII appears to have markedly different properties from mammalian CPSII (Asai et al. Mol. Biochem. Parasitol. 1983 7:89-100).

[0020] While T. gondii has a complete system for de novo pyrimidine biosynthesis, it only has a limited capacity to salvage pyrimidine bases. A biochemical survey of pyrimidine salvage enzymes supports the theory that all T. gondii pyrimidine salvage is funneled through uracil (Iltzsch, M. H. J. Euk. Micro. 1993 40:24-28). T. gondii has only three enzymes that are involved in salvage of pyrimidine nucleobases and nucleosides: cytidine/deoxycytidine deaminase, which deaminates cytidine and deoxycytidine; uridine phosphorylase, which catalyzes the reversible phosphorolysis of uridine, deoxyuridine, and thymidine; and uracil phosphoribosyltransferase (UPRT), which catalyzes the formation of UMP from uracil. The uridine phosphorylase and UPRT activities are the key salvage enzymes since pyrimidine salvage funnels all pyrimidine compounds first to uracil and then the UPRT activity yields UMP (Pfefferkorn, E. R. Expt. Parasitol. 1978 44: 26-35; Iltzsch, M. H. J. Euk. Micro. 1993 40: 24-28). The limited T. gondii pyrimidine salvage pathway is not required for viability. Mutations that abolish UPRT activity are tolerated and are equally viable to wild-type parasites in vitro and in vivo (Pfefferkorn, E. R. Expt. Parasitol. 1978 44:26-35; Donald, R. G. K. and Roos, D. S. Proc. Natl. Acad. Sci. USA. 1995 92:5749-5753). Furthermore, there is no available evidence that T. gondii actually salvages any pyrimidine bases from the host cell under normal in vivo or in vitro growth conditions.

[0021] The DNA sequence of carbamoyl phosphate synthetase II (cpsII) has now been cloned. To clone the CPSII gene from the RH strain of T. gondii, a forward degenerate primer: (CCN)(C/TTN)(GGN)(ATA/T/C)(CAT/C)(ACN)(GGN)(GAT/C) (SEQ ID NO:4) and a reverse degenerate primer: (T/CTC) (T/CTC) (A/CAA) (NGT) (T/CCT) (NCC) (G/TAT) (NGA) (CAT) (NAC) (SEQ ID NO:5), were designed from two stretches of amino acid sequence (PLGIHTGDSI; SEQ ID NO:6) and (GEVMSIGRTFEE; SEQ ID NO:7), respectively, which were well-conserved in the CPSII domain from various species. With these two primers, PCR amplification of strain RH single stranded cDNA derived from RH mRNA was performed in accordance with known procedures (Fox et. al Mol. Biochem. Parasitol. 1999 98: 93-103). A PCR product of the expected length, PCR 450 bp (see FIG. 1) was obtained. The 450 bp amplicon was excised from agarose, purified and cloned into the SS phage vector M13 mp9 in both orientations, for single-stranded sequencing using the dideoxy termination method.

[0022] The purified amplicon was then reamplified and used to probe lamba phage cDNA libraries from the NIH AIDS Reference and Reagent Center and a 1.2 Kb cDNA phagemid clone (pCPSII lc-1) was identified and transduced to bluescript plasmid for analysis via the manufacturer Stratagene's protocol. A 1.0 Kb EcoRI fragment from pCPS lc-1 was shotgunned into M13 mp9 and SS dideoxy sequenced. The sequences were found to align to those of the original 450 bp M13 mp9 clone and to have high homology to CPSII of other species. Separately, Southern blots of T. gondii genomic restriction digests were probed with the gel purified 450 bp fragment. This probe hybridized to several restriction fragments derived from RH parasite DNA including a unique band generated by HindIII (6.5 Kb) (see FIG. 1). Genomic libraries were then constructed in bluescript SKII⁺ phagemid vector that would contain the 6.5 Kb HindIII fragment and these genomic libraries were screened with the labeled 450 bp PCR derived CPSII cDNA. Positive clones containing the desired insert in both orientations were isolated. The ends of TgH 2-11 6.5 Kb clone were then dideoxy double stranded sequenced using T3 and T7 primers. Primers from the ends of the sequenced sections were used to sequence the remainder. The 6.5 Kb HindIII fragment was also used to screen additional T. gondii genomic southerns and three PstI fragments were identified. Subsequently, a PstI T. gondii genomic library was constructed using standard methods and probed with fragments from either end of TgH 211 plasmid to yield 7.5 Kb, 4.9 Kb, and 3.8 Kb PstI clones that matched the corresponding sizes on the southern. Locations of these clones within the genomic DNA and cDNA of T. gondii are depicted in FIG. 1.

[0023] Collectively, the RH genomic DNA clones obtained specify T. gondii cpsII amino acids that have significant homology to cpsII amino acid 304-1400 of the T. cruzi encoded cpsII protein. Alignment of the derived amino acid sequence of T. gondii CPSII as set forth in SEQ ID NO:3 was highest with the corresponding sequences of CPSII from the parasitic organisms, P. falciparum, B. babesia, and T. cruzi, approximately 35 to 45% amino acid homology.

[0024] The remainder of the cpsII genomic DNA clones were sequenced using a “walking” primer approach (see FIG. 1). For example, fragments of DNA at the 5′ end of clone 22-6-1 and the 3′ end of clone 18-7-1 (see FIG. 1) were used to identify additional fragments on Southern blot to obtain appropriate clones encoding the full genomic cpsII coding region plus flanking regulatory sequences. The full length genomic DNA sequence of T. gondii cpsII is depicted in SEQ ID NO:1. The cDNA of T. gondii is depicted in SEQ ID NO:2.

[0025] Mutant T. gondii were also prepared wherein CPSII activity was knocked out. Knock out of this enzymatic activity or any other de novo pyrimidine synthesis enzyme was predicted to produce a pyrimidine auxotroph that would be attenuated in mammals due to the inability of mammalian cells to provide the abundant pyrimidines needed by the parasite for growth. However, salvaging the growth of T. gondii purely by feeding pyrimidine compounds to the parasite in the growth medium was unpredictable. Thus, pyrimidine salvage in T. gondii was examined.

[0026] Initial experiments primarily involved an enzymatic analysis of drug resistant mutants and the incorporation of various pyrimidine analogs into T. gondii RNA and DNA as an indication of pyrimidine salvage when parasites were grown in either normal host or mutant host cells. All biochemical communications between the parasite and host cells cross the vacuolar membrane which is now known to contain “pores” that permit the passage of nucleobases ranging in molecular size from 112 daltons up to 244 daltons. The size of the pores is estimated to be approximately 1500 daltons. A T. gondii mutant resistant to 5-fluorodeoxyuridine (FUDR-1) had lost uracil phosphoribosyltransferase (UPRT), an enzyme which is absent in normal host cells (Pfefferkorn, E. R. Expt. Parasitol. 1978 44:26-35). Labeling of wild-type parasites or FUDR-1 parasites with [³H]deoxyuridine, [A] uridine, and [³H]uracil revealed a striking pattern of pyrimidine incorporation into host or parasite nucleic acids. [³H]deoxyuridine was incorporated into wild-type T. gondii and labeled the host cell nucleus (DNA only since deoxyuridine is mainly converted into TTP by host cell enzymes). FUDR-1 mutant parasites were not labeled with [³H]deoxyuridine. [³H]uridine was incorporated into wild-type parasites and labeled host DNA (nucleus) and host RNA (cytoplasm) (uridine is incorporated into the host cell UTP pool by host cell UTP pool by host enzymes). FUDR-1 mutant parasites were not labeled with [³H]uridine. [³H]uracil was incorporated into wild-type T. gondii and did not label either host DNA or RNA. FUDR-1 (UPRT knock-out) parasites were not labeled with [³H]uracil.

[0027] In addition to the labeling patterns observed, wild-type RH parasites did not incorporate labeled orotic acid, orotate, cytosine, cytidine, thymine, or thymidine nucleobases. These results suggest that none of the host pyrimidine nucleotide pool is available to the parasite. Similarly, since uracil only labels the parasite, due to the parasite UPRT which is absent in the host, the pyrimidine pools of the parasite are also unavailable to the host. Thus, there is no detectable pyrimidine traffic detected between the parasite and host.

[0028] Experiments to evaluate the feasibility of constructing pyrimidine auxotrophs of T. gondii were performed. Pyrimidine auxotrophy relies on the ability to feed mutant parasites a pyrimidine nucleobase, such as uracil, in culture medium in amounts that will restore parasite growth to near normal levels. Experiments were therefore conducted to measure whether uracil incorporation into parasites in culture could account for normal replication and normal growth rates. In these experiments, biochemically saturating amounts of [³H]uracil (25 μg/ml) were added to the growth medium and the quantitative incorporation of label into parasite RNA and DNA was determined over a four hour interval. It was calculated using known values that about 82% of the pyrimidines incorporated into parasite nucleic acids were derived from the uracil which was added to the growth medium as a supplement (Table 1).

[0029] Table 1: Uracil Incorporation Assay Results and Calculation of Uracil Incorporation

[0030] Time: Parasites were labeled for 4 hours.

[0031] Culture: Contained 2.09×10⁷ parasites.

[0032] Medium: Contained [³H]uracil at 25 μg per ml or 0.223 μmole per ml.

[0033] Specific activity of uracil: 34.3 CPM per pmole (CPM=counts per minute).

[0034] Results: The parasite culture incorporated 2.27×10⁵ CPM in 4 hours.

[0035] Calculation:

[0036] 1. Actual incorporation per parasite=0.11CPM per tachyzoite=0.00032 pmoles pyrimidine per tachyzoite per 4 hours.

[0037] 2. Tachyzoites contain 0.10 pg DNA per cell.

[0038] 3. Tachyzoites contain 0.50 pg nucleic acid per cell (The RNA:DNA ratio is 4:1).

[0039] 4. Toxoplasma nucleic acids contain 112:760 pyrimidine by weight, thus: tachyzoites contain 0.50×0.1476=0.074 pg of pyrimidine

[0040] 5. Pyrimidine molecular weight=112.

[0041] 6. Tachyzoites contain 0.074 pg/112/pg/pmole=0.00066 pmoles pyrimidine in nucleic acid.

[0042] 7. Tachyzoites double in 6 hours. This represents a 1.6-fold increase in the 4 hour labeling period, or equals the synthesis of 60% of nucleic acids in 4 hours.

[0043] 8. Theoretical 100% incorporation=60% of 0.00066 pmoles=0.00039 pmole pyrimidine incorporated per tachyzoite per 4 hours.

[0044] 9. Actual incorporation (0.00032 pmoles) therefore represents 82% of the theoretical maximum incorporation (0.00039 pmoles).

[0045] Conclusion: 82% of incorporated pyrimidines originate from uracil when it is added to medium.

[0046] An 82% efficiency of incorporation of exogenously added uracil into parasite nucleic acid was detected. However, the same pathway mediating this incorporation (UPRT) can be completely abolished with no effect on parasite growth rates in vitro or in vivo. These results indicate that the parasite may activate the uracil salvage pathway to obtain near normal levels of uracil directly from growth medium when it is available or when uracil is needed, or alternatively to completely rely upon de novo biosynthesis when uracil is unavailable extracellularly. These biochemical measurements supported the feasibility of constructing stable pyrimidine auxotrophs of T. gondii by constructing a knock out of a gene and enzyme activity of the de novo pathway.

[0047] A modified hit and run mutagenesis was devised for knocking out the T. gondii gene encoding CPSII. First, a new plasmid vector was developed for positive and negative selection analogous to the plasmid described by Fox et al. (Mol. Biochem. Parasitol. 1999 98: 93-103), except using the herpes simplex virus type I thymidine kinase (TK) gene instead of bacterial cytosine deaminase in the linker region of DHFR-TS. To create this plasmid two primers, a forward primer GGGAGATCTATGGCTTCGTACCCCGGCCATCAA (SEQ ID NO:8) and a reverse primer GGGGATCCTCAGTTAGCCTCCCCCATCTCCCG (SEQ ID NO:9) were used to PCR amplify via standard conditions the ganciclovir hypersensitive TK75 HSVTK allele (Black et al. Proc. Natl Acad. Sci. USA 1996 93: 3525-3529). The forward primer contains a BglII site and the reverse primer a BamHI site. Following BamHI and BglII digestion of the ˜1130 bp PCR product, the TK allele was ligated into plasmid pDHFRm2m3-FLG-TS which was digested at the unique BamHI site in the FLAG epitope linker. The TK PCR primers were designed to join with pDHFRm2m3-FLG-TS to produce an inframe insertion of TK between DHFR and TS in a plasmid called pDHFRm2m3-TK-TS, similar to previously described pDHFRm2m3-CD-TS plasmid (Fox et al. Mol. Biochem. Parasitol. 1999 98: 93-103). The trifunctional enzyme plasmid with TK was tested to confirm function of all three enzymes. Transfection of T. gondii with pDHFRm2m3-TK-TS and selection in 1 μM pyrimethamine produced parasites resistant to pyrimethamine. All subclones of T. gondii transfected with pDHFRm2m3-TK-TS (more than 100 clones of T. gondii) that are pyrimethamine resistant uniformly and concomitantly become sensitive to minute concentrations of ganciclovir. All T. gondii carrying a single allele of TK (or more than one allele) from pDHFRm2m3-TK-TS do not form plaques in 0.5 μM ganciclovir.

[0048] The TgH 2-11 clone of T. gondii CPSII was fused with the pDHFRm2m3-TK-TS plasmid to create a new plasmid suitable for modified hit and run mutagenesis. First, a 0.5 Kb segment of TgH 2-11 was removed from the 3′ end by digestion with BglII with BamHI. Resulting 2.6 and 1.2 kb DNA fragments were resolved in agarose and the 2.7 kb 3′ BamHI/BglII fragment was religated with the large DNA fragment from the same digest which contained the 5′ side of the HindIII fragment and the plasmid DNA. The correct orientation was mapped by restriction digestion. This created a modified HindIII fragment of CPSII gene with a central 1.2 Kb deletion between amino acids 723 and 1070 based on numbering from the T. cruzi CPSII gene. Finally, the trifunctional DHFR-TK-TS enzyme from pDHFRm2m3-TK-TS was added into the deleted HindIII (delta 1.2 Kb BamHI) plasmid by digestion of pDHFRm2m3-TK-TS with NheI and XbaI and ligation into the unique XbaI site of the deleted 1.2 Kb BamHI HindIII TgH 2-11 plasmid. A clone with inverted directionality of DHFR-TK-TS and CPSII expression was obtained and this plasmid was called p53KOX3-lR. The theory of targeting disruption of the endogenous T. gondii CPSI gene with p53KOX3-lR is that insertion of this plasmid by a single cross-over recombination would yield a C-terminal truncated CPSII with the 1.2 Kb BamHI deletion described above with a normal endogenous promoter but no untranslated 3′ regulatory region, and a duplicated cpsII allele with a N-terminal truncated (deleting everything before the HindII site at amino acid 663) CPSII and a normal non-translated 3′ regulatory region but no T. gondii promoter. Thus, single homologous crossover between truncated and deleted CPSII contained in p53KOX3-lR and the endogenous T. gondii locus would produce two mutant forms of CPSII with significant structural disruptions.

[0049] Wild type RH parasites were transfected with p53KOX3-lR and selected in the presence of 1 μM pyrimethamine and 200 μM uracil. Following lysis of the primary flask with p53KOX3-lR transfected parasites after 4 days of growth in 1 μM pyrimethamine plus 200 μM uracil, parasites were diluted 1:100 and inoculated into a second flask of fresh HFF cells under the same growth conditions. The second growth cycle is necessary for efficient selection of stable plasmid integration under pyrimethamine selection. Thus, transfected parasites must undergo approximately 25 cycles of replication prior to subcloning and screening for potential mutants. It is obvious that any mutant with any moderate or significant defect in growth rate would be quickly diluted in number by rapidly growing parasite in the mixed cultures. Following the second growth cycle of the primary transfection of p53KOX3-lR in pyrimethamine plus uracil medium, parasites were subcloned into a duet of 96 well trays with or without uracil supplementation. Individual wells were scored microscopically at 4-5 days post subcloning to mark wells with one viable parasite (a subclone) based on the presence of a single zone of parasite growth in that well. Typically 10 to 20 wells of a 96 well tray were successful subclones. Successful subclone wells were individually mixed by washing up and down with a 50 μl pipette to mix parasites to infect the whole HIFF monolayer in that well. Typically 3 further days of incubation produced total well lysis and many free infectious extracellular parasites. From these wells parasites were individually picked and inoculated (separate additions) into parallel wells of HFF cells in 96 well trays that contained the same growth medium (pyrimethamine plus uracil 200 μM) or trays only containing pyrimethamine 1 μM. If CPSII were knocked out in any of the T. gondii subclones a difference in growth rate could be detected by visual microscopic examination of identically inoculated wells. No less than 1 μl was tested at this point due to reliability of transfer and parasite number of inoculum. Thus, the concentration of residual uracil in the “no uracil” tray was actually still ˜1 μM. More than 800 subclones of T. gondii were eventually screened using the above assays, with more than 200 subclones being generated in each of four independent selections and transfection experiments with p53KOX3-lR. Following an initial assessment of growth rate estimate in the plus uracil or “minus uracil” condition, a number of putative clones were evaluated in a second test of uracil growth dependence. Following a second positive test of uracil growth dependence, a third test using 25 cm² HFF flask was performed under conditions of a uracil concentration less than 0.1 μM. From these selections four T. gondii mutants were obtained which had a quantitative assessment of at least a detectable growth dependency on addition of uracil to the growth medium. These were putative T. gondii uracil auxotrophs. One independent transfection produced mutant cps1, a second independent transfection produced mutant cps2, and a third independent transfection produced mutants cps3 and cps4. Each of these mutants was found to be highly sensitive to ganciclovir, loosing ability to form plaques in only 0.5 μM ganciclovir. The mutants were grown and genomic DNA was isolated from each mutant and wild type RH parasites from the contents of 2 or more 25 cm² flasks for each DNA isolation to document integration of targeting disruption plasmid p53KOX3-lR into the endogenous CPSII locus by homologous recombination. The plasmid p53KOX3-IR could form two general patterns of integration based on recombination either 5′ of the BamHI deletion, or recombination 3′ of the BamHI deletion. HindII digested cps1, cps2, cps3, cps4 and RH parasite genomic DNA was subjected to Southern blotting and hybridized to labeled gel purified 6.6 Kb HindIII fragment of TgH 2-11 encoding T. gondii CPSII sequences. A 5′ cpsII integration would produce at least fragment sizes of ˜6.5 Kb and 7.8 Kb following digestion with HindIII, whereas a 3′ cpsII integration site would produce at least fragments of 5.0 Kb and 7.8 Kb when digested with HindIII. If the plasmid were duplicated at the time of integration which is seen frequently with the pDHFRm2m3-TS plasmid backbone (Sullivan et al. Molecular and Biochemical Parasitol. 1999 103:1-14) then an additional fragment at 7.8 or 9.5 Kb could be generated by integration at endogenous CPSII. Each of the selected putative CPSII mutants had undergone an integration of plasmid p53KOX3-1R at either the 5′ location (cps1, cps2, cps3, or the 3′ location, cps4). Mutant cps4 had multiple bands between 7.8 and 9.5 Kb and additional bands at higher molecular weights suggesting integration of plasmid at CPSII and other loci. In contrast, mutants cps1, cps2 and cps3, obtained in independent transfections and selection, had identical patterns of hybridization to CPSII DNA suggesting that the targeting plasmid p53KOX3-IR only integrated into the 5′ site of the CPSII target region and each mutant had duplicated the plasmid DNA upon integration (the 9.5 Kb DNA band). Thus, successful targeting to and disruption of the T. gondii CPSII locus was demonstrated.

[0050] Each of the mutants (cps1, cps2, cps3, and cps4) have a phenotype of uracil growth dependence. However, all of these mutants are somewhat “leaky” in that there was not an absolute growth (replication) dependence on uracil addition to the growth medium for replication. Each of these mutants grows at a moderate (½ of normal) growth rate for the first 2 days following infection of a host cell producing vacuoles that contained 16 to 32 parasites by 3 days post infection. In contrast, RH parasites are lysed out of their primary vacuoles at this time (3 days, >64 parasites). However, the cps mutants slow after 3 days and many parasites never (about ⅓) break out of their primary vacuole. If the primary vacuole breaks, a few parasites can be detected at the site of infection but the infection site always involves a small zone of infection that never forms a visible plaque in a standard 7 day plaque assay. To quantitate growth of these mutants, HFF flasks were inoculated with cps1 or cps2 parasites (about a multiplicity of infection (MOI) of 1 parasite per 20 HFF cells). After 2 hours of attachment and invasion (all of these mutants have normal attachment and invasion phenotypes as scored by counting percent entered parasites into host cells as a function of time post-inoculation), different concentrations of different pyrimidine compound was added to parallel infected HFF flasks. As a function of time post pyrimidine addition (t=0 hour) the number of parasites per vacuole was scored for 50 vacuoles as described by Fox et al. (Mol. Biochem. Parasitol. 1999 98:93-103). The number of parasite doublings was calculated based on 1 parasite entering each primary vacuole. Thus, 1 doubling=2 parasites per vacuole, 3 doublings=8 parasites per vacuole, and 5 doublings=32 parasites per vacuole. The pyrimidine dependence of cps1 and cps2 replication (doublings of parasites in the vacuole) was plotted graphically. Relatively low concentrations of uracil, uridine, deoxyuridine, cytidine, and deoxycytidine completely rescued the growth rate of cps1 and cps2 mutants to wild type RH levels. This pattern of rescue is precisely consistent with the limited set of salvage enzymes available to T. gondii suggesting that these mutants have a defect in de novo pyrimidine synthesis that can be corrected by salvage of pyrimidines from exogenously supplied pyrimidines in growth medium in vitro. Cytosine, as expected, did not rescue at all. The response to thymine and thymidine was additionally informative about the cause of the growth defect in cps1 and cps2. Moderate concentrations of thymine or thymidine partially rescued the replication of cps1 and cps2, whereas very high concentrations of these pyrimidines did not rescue replication. This is believed to be caused by the putative defect in the cps1 and cps2 pyrimidine auxotrophs, that is a reduced “pool” size of UMP. If UMP pools (ultimately used for RNA and DNA synthesis) are lowered it follows that a resulting decrease in TMP pools is expected since UMP is the precursor of TMP in T. gondii and all other apicomplexan parasites which normally lack TK activity. However, since cps1 and cps2 now express a TK activity carried into the parasite by the p53KOX3-1R plasmid, exemplified by sensitivity of these mutants to ganciclovir (specific to HSV TK), feeding parasites either thymine or thymidine is expected to increase TMP pools. Thus, it appears that moderate levels of thymine or thymidine partially rescue growth of cps1 and cps2 by restoring TMP pools. These data indicate that there is indeed a defect in accumulation of UMP and TMP pools in the cps1 and cps2 mutants. The defect is most easily rescued by feeding the parasite pyrimidines that can be incorporated (uracil, uridine, deoxyuridine, cytidine, deoxycytidine) and can be partially rescued with thymine or thymidine (the TMP pool). Since the parasite has no mechanism to convert TMP back to UMP there is still a defect in the UMP pool in cps1 and cps2 even with added thymine or thymidine and rescue is never complete. The ability of cps1 and cps2 mutants to form plaques on HFF monolayers in the standard 7 day assay paralleled the pyrimidine dependence of parasite replication in vacuoles.

[0051] The cps1 and cps2 mutants were inoculated intraperitoneally (ip) into balb/c mice to measure parasite virulence compared to virulent RH parasites. Both mutant cps1 and cps2 had equal virulence as RH parasites in balb/c mice (Jackson Labs), killing all mice within 10 days of ip inoculation (group size was 4 mice per parasite strain). Only 100 parasites (˜50 PFU) of each parasite strain was needed to kill all mice in each group. This pattern of virulence can be understood by re-examining the pyrimidine dependence of cps1 and cps2 growth. Uridine is believed to be the pyrimidine responsible for virulence of cps1 and cps2 in mice. Only 5 μM uridine completely rescues normal plaque size of cps1 and cps2 in vitro. Plasma concentrations of uridine in mice are approximately 5 to 10 μM. Thus cps1 and cps2 grow normally in mice and are not attenuated at all.

[0052] It is believed that the single recombination into the CPSII locus only partially disrupted expression of CPSII activity in cps1 and cps2. Accordingly, cps1 and cps2 are not “complete” pyrimidine auxotrophs. Cps1 and cps2 were thus utilized as the parent strain background in which to select a more highly attenuated pyrimidine auxotroph mutant. Both the cps1 and cps2 mutants express a TK allele which was inserted into the CPSII locus. Hence, cps1 and cps2 mutants were grown for several generations in the absence of pyrimethamine and in the presence of 200 μM uracil. Then, approximately 1-2×10⁵ cps1 or cps2 parasites was inoculated into a 25 cm² HFF flask and selected negatively in the presence of 10 μM ganciclovir plus 200 μM uracil. This is 20 times the dose of ganciclovir necessary to completely block plaque formation of these mutants. After approximately 10 days, an outgrowth of viable parasites was observed for both the cps1 and cps2 selections. The parasites which were growing in ganciclovir plus uracil were subcloned in ganciclovir and uracil (same conditions) and individual clones, cps1-1 and cps2-1, were identified from each parent, respectively, for further analysis. The cps 1-1 and cps2-1 subclones were first tested for their sensitivity to pyrimethamine. The theory of negative selective in only ganciclovir is that a mutant that disrupts expression of the TK allele should simultaneously acquire sensitivity to pyrimethamine due to loss of the expression of the fused trifunctional DHFR-TK-TS transgene(s) inserted into the CPSII locus of cps1 and cps2. Indeed, loss of sensitivity to ganciclovir (10 μM) in cps1-1 and cps2-2 correlated perfectly with a gain of sensitivity to pyrimethamine (1 μM) in both replication and plaque assays.

[0053] Evaluation of the pyrimidine dependence of growth of cps1-1 and cps2-1 compared to the cps1 and cps2 parents, respectively, revealed that the newly selected mutants (cps 1-1 and cps2-1) were absolute pyrimidine auxotrophs. No pyrimidine compound at less than 25 μM could rescue plaque formation of cps1-1 or cps2-1. Further, only uracil and deoxyuridine provided significant growth rescue, and only in relatively high doses. Uridine was quite poor at rescue of plaque formation in cps1-1 and cps2-1. In pyrimidine concentrations up to 200 μM only uracil completely rescued plaque formation of cps1-1 and cps2-1. In addition, as expected from ganciclovir resistance (no TK expression) phenotype, no response was detected to thymine or thymidine.

[0054] A more detailed growth response to pyrimidine, measured as parasite replications (doublings) was performed for cps1-1 and cps2-1 and compared to the results previously obtained for cps1 and cps2. In the absence of added pyrimidines or the presence of even high concentrations of thymine, thymidine, deoxycytidine, cytidine, or cytosine, a cps1-1 or cps2-1 parasite that entered a vacuole in a host HFF cell remained as a single non-replicated parasite, not only in a 36 hour replication assay, but also upon continued incubation of infected cultures in vitro. Uridine rescue was poor, with a slow restoration of growth at very high amounts, >400 μM. Deoxyuridine rescue was significant, but again, full growth rate was not restored at any concentration of deoxyuridine. Rescue with uracil was robust, but only in a limited range of concentration. Full restoration of growth rate in cps1-1 and cps2-1 was possible only with uracil added between 200 and 400 μM. Lower concentrations of uracil rescued poorly and concentrations of uracil higher than ˜500 μM reduced the growth rate of cps1-1 and cps2-1 significantly. In fact, cps1-1 and cps2-1, as well as cps1 and cps2, do not even form plaques in 2000 or 4000 μM uracil, conditions with no effect on RH parasite plaques. This result is dichotomous and suggests that there is an intimate, regulatory loop in T. gondii pyrimidine salvage that is down regulated by very high concentrations of uracil. This phenotype can only be observed in T. gondii pyrimidine auxotroph mutants, not in wild type parasites with intact de novo pyrimidine synthesis pathways.

[0055] The cps1-1 and cps2-1 mutants were examined for virulence in balb/c mice. An ip administered inoculum of 100 parasites of either cps1-1 or cps2-1 had no measured virulence in balb/c mice, compared to the same dose of RH, cps1 or cps2 which were virulent. The avirulence of cps1-1 and cps2-1 correlates well with the pyrimidine dependence of parasite growth in vitro. The high concentrations of pyrimidines needed for growth of mutant cps1-1 and cps2-1 are simply not available in mammals such as mice. Other mammals including humans and other vertebrates are also not expected to have sufficiently high pyrimidine concentration to support growth of these mutants.

[0056] Higher dose virulence studies were also performed for the mutant cps1-1. Pyrimidine auxotroph cps1-1 was completely avirulent in Balb/c mice at doses equal to or greater than 10⁷ parasites delivered by ip inoculation.

[0057] The ability of the pyrimidine auxotroph mutants of the present invention to protect against infections was demonstrated. After 40 days ip inoculation of cps1-1 in balb/c mice, the same group of 4 mice were challenged with 200 parasites of the virulent RH strain (a 100% lethal dose) Mice originally inoculated with 10⁷ or 10⁵ cps1-1 parasites were completely protected from RH challenge. In contrast mice receiving only the lowest dose of 10³ cps1-1 parasites were completely unprotected from this RH parasite challenge. Thus, the pyrimidine auxotroph mutant given at appropriate dose is capable of protecting mice from lethal RH parasite challenge.

[0058] Safety of the pyrimidine auxotroph mutants of the present invention was also evaluated. A group of balb/c mice were inoculated with 10⁸ cps1-1 parasites and all survived at least 24 days post inoculation. A more rigorous test of safety was performed in immunocompromised mammals. Before the present invention, no T. gondii mutant had been isolated that would itself not kill gamma interferon homozygous knock-out mice (gko mice) (Jackson Labs, strain JR2286) (Radke, J R and White M W. Infection and Immunity 1999 67:5292-5297). Gamma interferon homozygous knock-out mice were inoculated with various doses of the pyrimidine auxotroph cps1-1 or a lethal low dose of RH parasites. Doses of cps1-1 (ip administered) at 10², 10 ⁴ and 10⁶ did not kill any of the 4 gamma interferon homozygous knock-out mice in each group, whereas all mice receiving RH parasites died within 8 days. Mutant cps2-1, was also avirulent in homozygous gamma interferon knock-out mice. Thus, the pyrimidine auxotroph mutants of the present invention are the first described T. gondii parasite isolates that are completely attenuated even in severely immunocompromised mice. The cps1-1 and cps2-1 mutants attach and invade as efficiently as wild type RH parasites in the absence or presence of pyrimidine in vitro in HFF cells. Thus the growth defect seen in immunocompromised mice is due to a block in intracellular replication only.

[0059] The pyrimidine growth dependence of mutant cps1-1 on the pyrimidine salvage pathway was further documented in thymidine interference experiments. Mutant cps1-1 plaques well in 250 μM uracil or deoxyuridine, but not in 1000 μM thymidine. Since thymidine at 1000 μM is known to inhibit approximately 90% of the parasite nucleoside phosphorylase activity specific for cleavage of deoxyuridine (Iltzsch, M. H. J. Euk. Micro. 1993 40:24-28), growth of cps1-1 was tested in combinations of 1000 μM thymidine and 250 μM uracil or 250 μM deoxyuridine. All pyrimidine salvage in T. gondii must pass through uracil and UPRT conversion of uracil to UMP. In contrast, thymidine has no effect on UPRT activity. Thus, if growth of cps1-1 were dependent on deoxyuridine supplementation then replication in this condition may be inhibited by co-supplementing with 1000 μM thymidine. It was found that thymidine did block deoxyuridine dependent growth of cps1-1 in these experiments by inhibiting nucleoside phosphorylase. However, thymidine did not affect UPRT or uracil dependent growth of cps1-1. Thus, when cps1-1 is grown in deoxyuridine the parasite strictly requires nucleoside phosphorylase activity to cleave deoxyuridine for growth. These data show cps1-1 and cps2-1 to have a marked defect in de novo pyrimidine synthesis and depleted UMP pools. Thus, cps1-1 and cps2-1 rely strictly on pyrimidine salvage enzymes for growth and further, the HFF host cell in vitro cannot supply sufficient pyrimidines for growth of cps1-1 or cps2-1. These data indicate that the pyrimidine auxotroph mutants cps1-1 and cps2-1 can be used in screening assays to identify compounds as inhibitors of various salvage enzymes when the replication of T. gondii is dependent on salvage pathways. Such potential inhibitors can only be identified using a pyrimidine auxotroph such as provided in the instant invention.

[0060] Survival, persistence, and reversion potential of pyrimidine auxotroph mutants cps1-1 and cps2-1 were also assessed. Ability of T. gondii mutants cps1-1 and cps2-1 to survive and persist intracellularly was determined in an in vitro survivability assay. From microscopic examination of cps1-1 and cps2-1, it is known that in the absence of pyrimidine addition the mutants attach and invade at normal efficiency and a single parasite can be observed in a small vacuole. With no pyrimidines added to growth medium the single parasite in the small vacuole remains as a non-replicated single parasite indefinitely. After 2 days of pyrimidine starvation, typically one bright blue (translucent) circular structure or 2 structures about 1 micron in diameter become apparent in many parasites and in most parasites by day 3 to day 4 of pyrimidine starvation. Thus, an assay was devised to measure whether the single non-replicating parasites inside the host cells were viable or non-viable. HFF flasks were inoculated with various parasite doses. At t=0 hours medium was changed, and pyrimidine starvation started. Then, at various time points (in days), cultures of pyrimidine starved cps1-1 and cps2-1 parasites were “rescued” by addition of 300 μM uracil. Incubation of rescued cultures was performed for 7 days in a plaque assay. All cultures were then examined for evidence of small micro-plaques by microscopic examination. Cultures were also stained for normal plaques and plaques were counted. The data from this assay indicates that parasites rapidly lose viability (loss of pyrimidine rescue). This loss roughly correlates with the appearance of the small bright blue circular structure in the intracellular non-replicating parasite that is starved of pyrimidines. Thus, simple culture of cps1-1 and cps2-1 in normal growth medium results in a pyrimidine starvation that efficiently kills intracellular cps1-1 and cps2-1 parasites. Thirty-two days of pyrimidine starvation was sufficient to kill at least 10⁶ PFU which was added to a single 25 cm² HFF flask. In these experiments it was also shown that addition of more than 2×10⁷ cps1-1 or cps2-1 parasites (MOI>10 parasites per HFF cell) to a single 25 cm² HFF flask resulted in all HFF cells becoming multiply infected with parasites each being a single parasite in an individual vacuole. Surprisingly even at these high MOI's of infection of HFF the host cell appeared perfectly normal, other than having 5 to 10 parasites within each cell on average. Thus, cps1-1 and cps2-1 also provide a useful strain of T. gondii to further analyze host-parasite interaction biology of obligate intracellular parasites. As demonstrated herein, these strains are particularly useful in further cell biological evaluation of the pyrimidine starvation phenotype or death phenotype.

[0061] To assess reversion, 106 to 10⁷ cps1-1 or cps2-1 parasites were periodically inoculated into HFF flasks supplemented with 5 μM uridine. This concentration of uridine is sufficient to rescue the parent strains (cps1 and cps2) of cps1-1 and cps2-1. However, it is insufficient to support any growth of cps1-1 or cps2-1. In multiple experiments involving a total of 5×10⁸ to 1×109 parasites of cps1-1 and cps2-1, no revertants were observed.

[0062] CPSII enzyme activity and thymidine kinase activity in parasite protein extracts derived from mutant or wild type parasites were also assessed. In these experiments, parasites were grown under appropriate conditions in multiple 25 cm² flasks or in 150 cm² flasks until lysis of the host monolayer. Extracellular parasites were purified through 3 micron nucleopore filters and parasites in parasite pellets were lysed in the presence of protease inhibitors to generate protein extracts for enzyme assays. The cpsII and TK enzyme activities in the various parasite extracts was determined in enzyme assays. The enzyme activity data indicates that the cps1 and cps2 mutants are partial knock-outs of cpsII activity compared to the activity measured in the wild type RH strain. Furthermore, as the bulk of data from pyrimidine rescue experiments indicated, no cpsII activity was detected in pyrimidine auxotroph mutants cps1-1 and cps2-1. Measurement of TK activity corresponded with previously determined sensitivity to ganciclovir. Parasites that were sensitive to ganciclovir had TK activity, whereas parasites that became resistant to ganciclovir lost TK activity. These measurements of cpsII enzyme activity confirm that the molecular defect of the cps mutants is primarily that of a loss of cpsII activity which results in blocking de novo synthesis of pyrimidines.

[0063] The sequences obtained from the cDNA and gDNA clones of T. gondii CPSII indicate that T. gondii has a CPSII organized like other apicomplexan CPSII enzymes. Accordingly, the same reasoning used to produce the T. gondii mutants is applicable to the generalized construction of pyrimidine auxotroph mutants in other apicomplexan parasites. Pyrimidine auxotroph mutants of other apicomplexan parasites are expected to provide protection against infection by apicomplexans in similar fashion to the T. gondii mutants exemplified herein. Thus, these apicomplesan pyrimidine auxotroph mutants can be administered to animals to immunize them against infection by apicomplexans.

[0064] To test the ability of the avirulent uracil auxotrophs of T. gondii to be act as a vaccine, the long-term protective immunity of the mutants was tested in vivo. BALB/c mice were challenged with a lethal dose of strain RH (200 tachyzoites) 40 days after inoculation with a single, intraperitoneal dose of the cps1-1 mutant strain of the present invention. The doses of the mutant strain were either 10³, 10⁴, 10⁵, 10⁶, or 10⁷ tachyzoites. When doses of the mutant exceeded 10,000 (10⁴) or more viable tachyzoites, long-term protective immunity was observed in the mice. In contrast, inoculation of mice with doses of less than 10,000 tachyzoites was much less effective at inducing a protective immune response in BALB/c mice. At a dose of 10³ mutant tachyzoites, there was zero percent survial at 10 days. At a dose of 10⁴ tachyzoites, survival was increased to 80 percent even out to 40 days. Survival was 100% at the three highest doses tested. When immune compromised mice were tested, although GKO mice still died after challenged with RH parasites, doses of 10⁶ or 10⁷ cps1-1 tachyzoites 30 days before challenge increased survial of the mice from 9 days (no cps1-1 treatment) to 11 days. These data demonstrated that an avirulent, easily produced, uracil auxotroph of T. gondii was a highly effective vaccine in mice and was able to confer protective immunity in immune competent animals.

[0065] The following nonlimiting examples are provided to further illustrate the present invention.

EXAMPLES Example 1 Parasite Material

[0066] Most of the work described herein used the RH strain of Toxoplasma gondii which is the most commonly used laboratory strain amongst Toxoplasma researchers (Pfefferkorn et al. Exp. Parasitol. 1976 39:365-376). Due to its long history of continuous passage in the laboratory, this strain is highly virulent in animals and grows rapidly in culture making it ideal for obtaining large amounts of material. However, it has lost the ability to go through the complete sexual cycle in cats. Parasites were grown in vitro in monolayers of cultured human foreskin fibroblasts (HFF) in accordance with well known procedures, for example, Fox et al. Mol. Biochem. Parasitol. 1999 98:93-103. Typically, using the RH strain, infected cultures were maintained by seeding uninfected monolayers; at about a 1:50 dilution every 48-72 hours. This yields about 10⁹ parasites from three T175 flasks of infected cultures. Parasites were harvested just as host lysis occurred filter purifying parasites through 3 micron nucleopore filters. Detailed methods for growth, harvesting, passage, purification of tachyzoite parasites, storage, and replication assays of T. gondii are routine and well known, for example, Roos et al. Meth. Microb. Path. 1994 45:23-65, and Fox et al. Mol. Biochem. Parasitol. 1999 98:93-103. All media reagents were purchased from Gibco-BRL (Rockville, Md.), Bio Whittaker (Walkersville, Md.) and Sigma (St. Louis, Mo.).

Example 2 Chemicals and Enzyme Assays

[0067] Most chemical or biochemical reagents were purchased from Sigma (St. Louis, Mo.). Ganciclovir was obtained from Roche Labs, Nutley, N.J. The linked assay system for cpsII activity was performed in accordance with known methods, for example, Asai et al. Mol. Biochem. Parasitol. 1983 7:89-100 and Hill et al. Mol. Biochem. Parasitol. 1981 2:123-134. For cpsII assays parasites were lysed in M-PER extraction buffer (Pierce Inc., Rockford, Ill.) or by osmotic shock in 4 volumes (w/v) of 10 mM potassium phosphate (pH 7), 0.05 mM dithiothreitol and protease inhibitors antipain, leupeptin, chymostatin, and pepstatin A, each at 0.1 mM. After 1 to 2 minutes of lysis, glycerol 7.5% (w/v) was added back to the extracts. The lysed parasite extracts were centrifuged at 20,000× g for 15 minutes and the supernatants used in cpsII enzyme assay. CpsII reaction assays contained 50 mM HEPES (pH 7.2), 10% (w/v) glycerol, 20 mM MgCl₂, 20 mM ATP, 3 mM L-glutamine, 0.5 mM L-ornithine, 10 mM KCl, 0.05 mM dithiothreitol, 1 unit ornithine carbamyl transferase, 10 mM bi[¹⁴C]carbonate(1 μCi/μM) and extract in a final volume of 0.1 ml. Sodium bi[¹⁴C]carbonate was 30-60 mCi/mmol and obtained from ICN. Reactions were run for 30 minutes at 37° C. and then terminated by addition of 10 μl of 5 M formic acid. A small piece of solid CO₂ was dropped into the stopped reaction and excess CO₂ was removed by standing the open solution in a fume hood. Reaction volumes were removed, dried and redissolved in 0.1 ml water prior to addition of liquiscint scintillant and counting of [¹⁴C] in a Beckman scintillation counter.

[0068] Thymidine kinase assays were performed in accordance with known methods, for example, Maga et al. (Biochemical Journal 1994 302:279-282). Briefly, parasite extracts were lysed by sonication (1 minute, kontes microtip) or in M-PER extraction buffer plus a cocktail of protease inhibitors (antipain, leupeptin, chymostatin, and pepstatin A; 10 μg each) and 1 mM phenylmethylsulfonyl fluoride. TK assays were run in a 50 μl volume at 37° C. for 30 minutes in a mixture containing 30 mM potassium HEPES (pH 7.5), 6 mM ATP, 6 mM MgCl₂, 0.5 mM dithiothreitol and 3.3 μM [³H]Thymidine (20-40 Ci/mmol from ICN). The reaction was terminated by transferring 25 μl of the incubation mixture to DE81 ion exchange paper (Whatman, Clifton, N.J.). The spotted paper was washed in 1 mM ammonium formate (pH 3.6) to remove unconverted nucleoside, distilled water, and then a final ethanol wash prior to drying of the paper and scintillation counting in liquiscint. Protein determination for parasite protein extracts was determined using Bio-Rad protein assay reagents and bovine serum albumin in accordance with standard procedures (Bio-Rad, Hercules, Calif.).

Example 3 Molecular Methods

[0069] Molecular methods including DNA isolation, restriction, Southern blotting, hybridization, and PCR reactions used herein are all well known, for example, Bzik et al. Proc. Natl. Acad. Sci. USA 1987 84:8360-8364 and Fox et al. Mol. Biochem. Parasitol. 1999 98:93-103. Transfection of T. gondii was also performed in accordance with routine procedures (Roos et al. Meth. Microb. Path. 1994 45:23-65 and Fox et al. Mol. Biochem. Parasitol. 1999 98:93-103). The gene libraries were developed from HindII or PstI digested genomic DNA cloned into bluescript KSII digested with the same enzyme and treated with alkaline phosphatase prior to ligation with T. gondii DNA fragments. Libraries were manipulated in accordance with known methods (Bzik et al. Proc. Natl. Acad. Sci. USA 1987 84:8360-8364). Total mRNA was isolated from T. gondii using TRIZOL-LS reagent (Gibco-BRL, Rockville, Md.) and mRNA was converted to cDNA using a cDNA kit from Pharmacia (Piscataway, N.J.) with polydT or random hexamers primers. DNA sequencing was done using classical dideoxy chain termination or automated sequencing using fluorescent dyes (ABI sequencer, Foster City, Calif.). DNA sequences were analyzed using the MacVector suite of programs (Oxford Molecular, Beaverton, Oreg.) and resources at NCBI, such as blast search. The DHFRm2m3-TS allele was obtained from the NIH AIDS Reference and Reagent Center (Rockville, Md.). The TK75 allele which was described by Black et al. Proc. Natl Acad. Sci. USA 1996 93:3525-3529 was obtained from Darwin (Seattle, Wash.). Bluescript plasmid was from Stratagene (La Jolla, Calif.). Restriction enzymes, nucleic acid modifying enzymes and transfer membranes were from Boehringer Mannheim, Indianapolis, Ind.

Example 4 Experimental Infection and Animal Studies

[0070] Balb/c inbred mice and balb/c mice bearing a homozygous knock-out of interferon gamma (gko) were obtained from Jackson Labs (Bar Harbor, Me.). Tachyzoite parasites were aseptically handled and purified from freshly lysed monolayers of infected HFF cells through a sterilized 3 micron polycarbonate membrane (Nucleopore, Cambridge, Mass.). Parasite concentration was scored microscopically in a hemocytometer. Purified parasites were pelleted at 1500 g for 10 minutes and washed in sterile EMEM media with no supplements and without disturbing the parasite pellet. The centrifuge tube was centrifuged once more for 2 minutes and the supernatant removed and replaced with EMEM media containing no supplements in a volume of EMEM to give a 10 times higher concentration (per/ml) of parasites than the highest dose. This was done so inoculation of 0.1 ml of this solution would equal the highest parasite dose. Parasites were gently resuspended in sterile EMEM (no additions). Mice, in groups of four, were inoculated with appropriate doses of tachyzoite parasites in EMEM. Following inoculation of mice the residual volume of unused tachyzoite parasites was returned to the sterile hood and dilutions were made to represent 200 and 400 parasite plaques on 25 cm² HFF flasks assuming 100% recovery of parasites after centrifugation/resuspension and 100% percent viability. Then, following a 7 day plaque assay, actual plaques were counted, post-inoculation of mice, and the percent viable PFU ratio to parasite counts in the hemocytometer were determined microscopically in every experimental infection. Uniformly, all of the mutants described herein as well as RH parasites always fell in the range of 0.4 to 0.6 viable PFU per parasite counted using these conditions. Following inoculation of mice, mice were observed daily for signs of infection (or distress) or death.

1 9 1 24023 DNA Toxoplasma gondii 1 atgcctcaca gtggagggcg gagagctgtt gctcccattt accctctcga tctggcaggt 60 cagtccgccg tttcgttcag acttccttct cgtctgggtt ctttgtttca cacgcctggc 120 cgcgtctcct ctccgcttct tggtgtgcag cctcggtttc tcccctttga tcagctgtct 180 cggttgcgct tccgccccgt gcgtcgcctt ccgtgtttgc ttccaatttt ctcctggctt 240 gctcgtgtgt tcgcgcccct ccggggagac cggcctgtct gctgccgaca gagaggcagc 300 tgtgaagggc gtgatcatca actgtctccg acggagagac acgacgtctg tgatgcaagc 360 aaatgagcgc gtgtatgcac aggtacccgc gcatactgaa atattttcgt atctgcagat 420 ccacaggcgc atgcatgcgc ccaactgtac ccacgcgtgt ttctacatag ttgtggagag 480 gcacatgcgt ctgcatgtgt gcacgttgtc tattcttgcg aacgataaac ctggtggcga 540 tccgtgtgtt attttcaaga agtgatttcg acgcaggcca tctcgctcgt cgctcgtttc 600 ctgtgtttgt cggctgctcg caggacgtct gagacctgca atgctggtgt tagccgatgg 660 gactgagttt ctcggatact ccttcggcta cccaggcagt gtgggaggcg aggtcgtttt 720 caacactggt acgtttttct cgaatttgtc cagaaacgct gacgtttggc gtctctcctc 780 tccagaaagg gtgcattcgg tctatccgct gtgtgctgca gcgattggtc ctcctcttac 840 aagcgcgtac accaccctat gcagcctcat gcaccgccat ctgtcaacgc gtgtggggac 900 cgccaccaca cgcccatgta tctaccttcg ataaacatat ttatgcatat atatatatat 960 atatagcata tatatatata tatatatagc atatatatat atatatatat gcatgtagat 1020 actcaaaatg catgcatatt ggtacgtctg ttcacctgta tttttctgcg tgataattag 1080 atacccctgg gttgcgtcac catgagctgt gtatcgttct gggtgcatgc gttgttgcgg 1140 gagtgttcgt gcgtcgggaa aggtagtggc cgacttcttg tctttggcgt ggttaggtat 1200 ggtcggctac cccgagtctc tgacggatcc ttcgtacgag gggcagatcc tcgttctcac 1260 ataccctctc atcggcaact atggcgttcc ctcttcggaa aaagtgagag cagacagcaa 1320 gaaaacgaag agactagcag aaccccgtac ttcgtggctg atccacatca gtgagagtcg 1380 aggagggaga gtcggatttc tcttgcgacg caacgtcaca ggaaagcaag tctggcaggg 1440 gtctccgctt tctcacatgc cgaatgcgca cacaaatcat tcatacgtca ctacaaaact 1500 gagtcctacg tgagaagagc aacgtcacct ctccgtgaga catatacgtg tttctatata 1560 catatataca tattatgtat atatttatat tcaaatatat atatatatat atatatcaat 1620 gtgcatatct aagtttatat atgaacgttc atctgtcttt cgggagagta tttccctaaa 1680 tggcagatgc taagacgcct gtacacctgc gtgcaaaggt gtttacgcgg gtgtctacac 1740 gtgagcgaag tgattgctac acacatgtat atatatatat atatatgtat gtcgctttac 1800 agtgtttgtt tttctgtaca tctaaagtcg tctaggcatc gatatgcgat gtgcatttca 1860 gcgtatttcg tgtgtttcat ttccactctt caggatgagc atggcctgcc gaaatacttt 1920 gagggcgacc gcatttacgt tcgcgctctc gttgtggcgg actacgacaa cgcagccgtg 1980 acggcacact ttcgtgcaga gaacagcctc agtgcttgga tgaacactca caaagtcccg 2040 gcgattgcag gtgcgaaaac atcgaggccg aagtgtctgt agtgtcagat gcgcctctgg 2100 acacgacatc ctctttcgat gcttgtcttt gattttcact taattttctc ttcgcaagtc 2160 tgcgaaggaa cgcctgtctg tacatctcga tgcccaggtg gctttctcgg ccatttggag 2220 gaactgtctt ggatccgcgt agtaggcatg tatgagggag cagcttctct ttcttctgaa 2280 ttgtgttcca cttgtaagtc ggttcgacca cgagcagtca agaggctctt accgtgccac 2340 cgagtcaacg tcgcccatca cagaccggct tttgaatgcc tttttcttca ggctccatta 2400 atgcacgtct cactgaatcc gtgctcgtca atttggacag ctagatctgt gtagtcccta 2460 gagactaact tttggaggga gactaacaat acagctaggt tgctctacct cggctatgtt 2520 taacgcatag ttcacggatc actgttgcca ctggtcctta cagagagagc acacgactgc 2580 tcacgtgctt gtcatggaga cacatctcga tcgtgtatgt ttcacttcag ttctgcagag 2640 ccgttcagtg tatgtctgcc atgacgggga ggggtatctc aagggtgtat tttgaactgt 2700 atttccacgg tgtacggggc ttgaagtact ggcgcatcta tgtctggagg acgggacgtg 2760 gtttagttcg tgtctcagtg ctcaacagcg tccggatctc tggcatgctg ttgccatcct 2820 gttagttgct ggccttcgcg gctactcttt ctcctttagg tgcacctcca gtgtctccag 2880 ttcagctggt gttcccttgc cgactgttgc tgctctgtca gggctttgta ggtccccgcc 2940 tcactctcgt ttccgcttct ctgttttctg cgtccgtgtg tgtctcacct cttcctcttc 3000 gtttccatct cttttcttgt ctcgcctttc cacggctctc gtttgctctt gaaacgctgt 3060 cggttgtcgt cgttccgcct cgttctctat tcggctctat cttcgtcgtt cgtcttttgc 3120 ttcttttcga cttcccgact cctgcctgtt tccggctgta tcgttttctt tttcaaggag 3180 tcgacacgcg agcgttgacc aagcacctgc gcgaggtcgg ctgcatgctg ggcaagatcg 3240 tcgtcctgag cgaagaagaa gagcgtcgat ccggcttgtc gctctcggct ctcgccgcgc 3300 ttccctcagc gactgcagca gagcaacgag gagagaacga cgcgacggtg acgcccgaca 3360 aagcagaggc ccgcctaaga gtggagaggc gacaagcagc gctcacgatg tgggaggagg 3420 cgatccgcaa caaggcgaag aacctgccat gggaagaccc caacaaagac aacctcgtcg 3480 ccctcgtttc gcgaaaagaa gtgcgcgtgt acaaatctac tgtcgtggat ccggtgagtg 3540 acagagagcc cagggaaaga cgtttcacgt gcgaaagcga aacgcagttt ccacagtcct 3600 tgtttagatt tagcgtggga catgcacaag ttgggattct gcggaatgcc gctatctggg 3660 gaggggagta tagacgccga gttcaactcc tggcttcaat ctcccctcaa tcgaggcgta 3720 gcgcaacgcg ctcgctttgc actggtttcg ccgccccgga ggtccgtgct gagctgtacg 3780 tacatccggg gtgtgtatgc ccgttgcgat cgcgtttgag tgttttcggg gtctgactgt 3840 gcgtgtccgg ggcctcccgg gcggcgcctg tcgaatgtgc ggctcggctt tgcccgcctt 3900 ctttctccaa agtgtgtctg gactgccttt ctgtgttctg tcggaatctc aagtctgggc 3960 tgtcggtttc gttgcctgaa tctgcagaat ctccgcgacg tcctcatcct ctgcgtggac 4020 tgcgggatga aatacaacat ctaccgccag cttctccata gcaaattcga gcactgcaac 4080 atcattctca aggtacagct gtcgctgctc tgactgcatt gactttgaaa ctctcattcc 4140 tgatctgtta gctctcccgg cagttcgctt gtattttctg tttcctgtgg cgcccacccg 4200 tcaattcccc tttctgcggc gccgagcgct cttcagctgg tactgggaaa tggagatgtg 4260 tgtccagcag tatcaagaca tacagaagta tactgatgtg tacacgtgaa tctccattct 4320 gtttatgcat gcatgtctct ctctctctct ctctatatat atatatatat ttgtacatgt 4380 atttatgtgt gtgcgtgcgt ttgaatataa gtacgtatta tctacaagtt tgcatgtttc 4440 cgtacgaatg tccgcaggcg tgtgtgtctg gttacatgcc gctgaatctc actattcaat 4500 taaacagttg agtgtggaga ggtaagcgag actgtgactg cgcaggtgtg aaaccgttca 4560 ggagcgcatg cgctgtgcgt gtctctcagg tggtgccgtg ggatttcgac tttggcaacg 4620 acgaatttga cgggctcttc atcagcaacg gtccaggcga ccctgagaga tgcgaaaaaa 4680 cagttgctaa cattcggtgt gtgctgcaga gaaaagccga ttcgttcgcc agagtcagga 4740 acagcacagt ggcgcatttc catttccgtc ttcgctgtag acacgcaaaa ccatcgcgat 4800 ttgcagattg gttgagcttg ctctctgagt cgcgggaaac tgttccttcc gttccatggc 4860 gacccaggca cagagaagcg tgcatgcaaa aaacaacgtg gagtctctcc gttttgtctc 4920 tgctaactta gtataacttt agacccggca aacagcgaca tgcacgagtt aaacgcgtag 4980 tccatctctt acatgaaatg gactctttag aaagcgcaag acggtgcacg ctacaccagc 5040 ctcgttcgta ggcttgcgta ttgagttcac gcgattgaac accgaattgt cgaggcggga 5100 agttcgcgtc taccacatat tcatctgagt tccatctcgg gttgctccgg ttcgggccaa 5160 ggtgactgga atgcccggtg gctgccgggt actatgtgct tccccgcgga tctcccatgt 5220 tctcttgtgt gggcagactg cgcagcactg ctggtggctg cgtaggttca tgcccttaca 5280 atgtaaatcc cttttctacc gttcgttctt cctcccgttt tcagacgcgt catggagcga 5340 aagatcccca tcttcggcat ctgcctagga aaccaacttc ttgccctggc tgccggcgcg 5400 agaacgtaca aaatgaaata cggaaacaga ggtaagcgtt gtcgttcgtc ggtcacactg 5460 attgtacgcc gtttcaggtg tacgtacacc tctttcaccg gcagcgaggc gccggtccag 5520 ggagcgtccc gcgacgtggg tggcaggcca gtgactagcg acggcgaggc gaagagggaa 5580 aatagcatct ccggactctc atttctgttt tgccgttgca ggaatgaatc agccggtgat 5640 cgacttgcga acgtcgagat gctacatcac accccagaac catggctttg ccgtcgacga 5700 gagtaagcgg cgacaacatt ccatctgcga aatctaggtg ccatgacctc catatgccgt 5760 tatcgtagac ataatgttga tatgtagaat gcatatggat acgtcgagag aggtcagatt 5820 cacttttgta gatgtagacg gctataaatc aaagtggttc atgcatctgc tgttggttgt 5880 attttgacag cattgtgaaa gggagtggtg ttcgatagaa cgcaaatgtg acgcaattgt 5940 atccgtaaga ccctgagttt cattataagt aggtattgcc tctgtacaaa tgatccgcga 6000 gccagaactg tataactcaa accgaataaa cagagtgtct gtcgctgtga atacgaatgg 6060 taacagtaat ccatatattg cgcctagaac gtaaccgatg tggaataacg taaaaatgcg 6120 tgtttgagcc ctccacgtca gcggtctgtc gattgtgaat tagcgaagcc gacccgtcga 6180 tgaagttcaa cagtcagcca gatattcagt ctctagaacc tccacaaagg atgatgtcct 6240 ccaggtagcg aagataccaa ctgtggtgtt ggagaatggc gtttcaaagc cggtagcgtt 6300 gcagacactc ttgtgtcctc gtgggagtcc gtgttcgagg cgggcagttg ctacagcaag 6360 tagatgcgta gaacgaagcg agacctccac gcggggattt accttttgac atcagttctg 6420 gaagactgca gatcctttgc acagatgcaa tatctgctta cggtgtggcg cttacaatac 6480 atggtcgagc tatgctcctg tcggtctcag tgcggccttc gtcagatgac agatgtggac 6540 acctgcctat atgaccctgt gttgaacctc tcgccgtttc tgcaggcacg ctgcctcgag 6600 atttcctgcc gctctttgta aatgcaaacg accgttcgaa cgaaggcatc atccatcgca 6660 cgctgccttt tttctctgca cagttccacc cagaggcgtc aggtaaggcg ggcgatactt 6720 cttcgactga aataccgacg ttgcagatca gcgacatctc tttccgttgg cgtcgtttca 6780 atgatcagtg cttgaaggca tcttggcagc gtttcgtcgg accaatacgg cggaactgga 6840 gctcgacggt acaaggaatc tgtgactgcc gatgctcttc tcgatgatgc aggggcgaca 6900 gttcctttca tgagggaaac atgtgcttgt gtcatcagtt cagttcctca taactggagg 6960 catctgttgg gtcttaaata aagccgcccg ctaagaagga tgctgccttg cgacgcaact 7020 cgtgtgtcac caactgcatc gcgatgggag agtttttcct ctgagacaaa acgaggatgg 7080 acctccgaag ttcgtgtacg cagtctgcga gtcagtgggg tgccgacgca cgagacgaag 7140 acgagccact cagagattat tgtttctcac ttttctgcct cggcgaagaa gcagcgcata 7200 cccatcggtg cccctccgct gggcgtctcg tgcgttccct gtcgctggcg cggcttcgtc 7260 aacacagtgc accgattttt tcttctgctc gtttgtgaca acctagagag ctccagtgag 7320 atcgaggagt ggcgcgagat gtgagtttca cgcggtggag gccagatgat gtttcgtcaa 7380 gagctgcgcc gcagtctacc acgcagcgca gaccccgtgg ggtgtgtcct tcgcgcgatt 7440 ctttcctgga gtctgtgggg tgtttataca ctcggcgtcc ctctgtctgt gccttctggc 7500 tcaggtggtc cgacagacac gttttactta tttggcgact tcatcgcctc gattatgaag 7560 gcgcagacgc tgaagcaggt ccacacgact ccgttctcct ttccgcagaa gttccagaaa 7620 gttctgcttc tcggtaaggc cggtgttcct cccgcatctt gagggaaggc gagttctttt 7680 aaagtgcaga aagccctttg cgggggtcat cagagaagga acgccatcgg ctgcatcctt 7740 cttggtttct cgcaaatgcg tctgtggctt ggccgtcgcg tggttccttc tgaacgcccg 7800 tgtggaggtt tcccgacgct gtcatctctg ccaaggtgtc gtcgtggacg ttcaagagtg 7860 cgagagcggc cctgccgact gtcgcagaga gcgcggctca tgtcatgtct cccttgtgca 7920 ttctccctga gcttttcgcg ggctctcttt cgacctctgt ctccgccggg atcatctgtt 7980 taggaggacc gtgtcgtggt gactgtgccg gaggctctgc tcgctcaagt gaggaggtcg 8040 gggtaaggcg ggaagtcggc tgtgtgtgcg tggtttattt gcttcgtagg gagcggaggc 8100 ctgagcatcg gccaagccgg ggagttcgac tacagcggct ctcaggcgat aaaggcgctg 8160 aaagagcaga acatctttgt cgtcgtggtg aaccctaaca tcgccacggt gcagaccagc 8220 cagcacatgg ccgaccgggt gcgttgaccg cgcagacgga ttgcgcagag tggcgtcgag 8280 ggagcgcgaa cgaaaaagga ggacgcagac gccagagaag acacagagaa tcagagagac 8340 agcgagagac agcgagagac agacagcgag acagaagatc aatcgggagg caaggaggag 8400 agcgaggtag agagaaaccg cgagaaacac agagaggagc agagagctaa caagacagaa 8460 acaaagcgtg gtgcaggaag acgcagatga gagggagaga cggagcccag agcagagaca 8520 gaaagacaga gcaaagagag acacagacag aacagagaga gagagataag ggtggaggtg 8580 aaggaataaa ggcggggctt gagcgaacgg tgaagcatta ggccgtggaa ggtgacgaaa 8640 gtgcgatgga ggcaggatgg tctttgtgag gccttctttg tcggaagaag agagtggaca 8700 ccacgtattt ccactgctgc gttgcgtaac gcgtttatga gagagtactg cggttcccca 8760 gagactggcg gaaaccaagg agtcggcagg ctttctcggg tctctctccc ctctgcgttg 8820 tgagtttcct aacgtctgtc gacttcggga agtccgaaac tctccggaga agacacacgc 8880 aactccaaac tgcgagtgga gtcgagccga tccagtcgag tagtagcttg catgaaatgt 8940 gtcgagccgg gtgcatgcaa ttcatttttt caggtgtact tcctgcccgt cacggatgag 9000 ttcgtgacga aagtcatcga aaaggaaatg cccgacggca ttctctgcac attcggaggc 9060 caggtgcgtt tgcgtgtgtg caacggcttt ttcctcgatg aacgtaacta aatgcgcgaa 9120 gatataacga ggcctaggca ctcgcaaatg gacaatccat ccatatgcat atatattcat 9180 atatatgcat gtttaatata tatatatata tatatatata tatataataa tatgcgtatg 9240 gggctggcca ttgaggagat atgtatgcag ctgttcagag gagtagcgta ggcgaacacg 9300 tttgcatgca tagagttctg gacgaagcac gtgatcgtgc ggatatatgt aaatgaggtt 9360 gtgggtgtat gtggggacag cgatatctgg acagggtacg gctttttttt tcactttatg 9420 gcatgttcag acggccctca actgcgctgt gaaactccac gaacaaggcg tcctggcaaa 9480 attcggctgc aaaatcctcg gcagtccaat cgaagtaaga atgtattcat atatatacat 9540 ccatatatat atatatatat atatatatat tcgtaactgc ataaatgcac atattcatag 9600 tgatacatat atatatgcac atagacatat gcaagtacat ccgcgcacac atatgtccat 9660 atatgtgtgt atatccatat ataaatatat atccatatat atatatatat atatatatgt 9720 agagaaatgt gtgtgtgtat cagtgcacgt tacgatgcac aaatttgtat actggtgtgt 9780 atttaggtat ccgcgcattt cgagtttcgt gggaagcacg cggtgtcttg tttgtctttt 9840 ttaggcgatc attgcgactg aggatcgaaa ggtgtttgcg gcgaagctgg aagaaatcgg 9900 agaaaaagtg gcggagagcg cggccgcgac aaacacggaa gaagctgtgc aagcggcgaa 9960 ggccattggc taccccgtcc tcattcgcgc cgccttcgca ctcggtcagc caaagaagag 10020 accggggagt gaagacgagc gaagaaaagg ggcgcaaggt cgacgagagc aatgagagga 10080 gacccagaaa aggcgcacac agaacggatg cagacggaaa cagacgaggc gacaaaagag 10140 gcagtcgatg acagagaaga atgcgaggga gacggaagca ccgaagacga agggaagaga 10200 actggccaga aacgaaggat acggatttca cgttcaagtg atgtcaactt gcgtgtggac 10260 tatcgcaggt gggctcggat ctgggttcgc cgaggacgag gagaccgtcc gacgcatttg 10320 caaggaagcc ttctcccatt cttctcaggt ccggtcaact tctcgtagtg catgcgtata 10380 cgcacatcag agtaaaattt gcatatatat atatatatat atataagtat atgtatgcac 10440 acatatatgt ttcagttctt atctgcgggt gtacttgtgc atgtccgcac cggcgtcgtg 10500 tgggcagatg tgaacgtctg gagagagagg tcgcccgttc tgaatgcgcg tgcatgcgtt 10560 tctgacaggc gtgtctgcat ggctgcggaa gccgaatgaa accccacact tccgaaggaa 10620 tttcgcgttt cagccggttc gtttgcaggc cgagtgtcgt cggggaggct tcctcgttgt 10680 gttggtgtgt gccggtccag tggttctcgc gcgaagcccc gagtgcgtcc cctataagac 10740 tgaaaagcgc caagtcgagc tggcggaact ctgagaattt acgttttttc aggttttcgt 10800 ggacaaaagc ctgaagggct ggaaggaggt ggagtacgaa gtcgttcgcg actgcaagaa 10860 caactgcatc accgtctgca acatggagaa cttggatccc ctcggtgcgt ctcgtctgtg 10920 tgcatttgcc gtgtttgctc ttcaactgtg gcttctcagc tctgtcgagg ggtgcgctgc 10980 ggaggctcgc tgtacaccac gaattgtttc tggcctctct gttaacgagc gttctgaaac 11040 gaatccccac acaagtgcat gctccctctc gtcctctcgc tgcttgactc tgtcgctgcg 11100 ggggaatccc tcgtaccgtg ctctcgctgt gacgacctct gagtggacgc gtctctctcg 11160 gacttctctt tgtctctcgc cagacgcagt gattccaagt ctctctcttt ttgtgcagcg 11220 ctgtctctga cgaacgctgt ctatcggcgt atctctcctt ctccgcttct ccagagcttg 11280 gcacttctct gtataaagat ttacatatat atatatatat atatatatat atatatatat 11340 atatatatat atatttgaat gtttttgtat atgcactcca tctggataat tcagtcgtcg 11400 aactctattg tcacagcgtt ttggtcactt aaaccggcgt ccttcgtcga tggtttgcgc 11460 atgcgctttt tgcgtccatg tctgtacacc cgcgtgtgga ttttttcccc tcaggcatcc 11520 acacgggaga ttcgattgtc gttgctcctt cgcaggtgag ctgtcttcgc ttgtgttttt 11580 ctgtttttca tctctcttta tacatttctc ggtccgatat ttctgctctc tcatggcctc 11640 tcttttgcca ttttcctcgt tgttttctct tatccctcgt tcttcctctt gttatgtctt 11700 cttcttatcc tttgttatct tttgtccgcg ttggtctatt gttgtctccg cttcaaatcc 11760 cttcgtctcc cacacaagcg cgcgttttct tctttgctct ctctcttcag acgctgtcta 11820 acgaggacta ctaccgcctg agagataccg cgctgaaggt gattcgtcac ttcggcatcg 11880 tcggcgaatg caacatccaa tacgcgctcg accctaactc ggagaaatac tacatcgtcg 11940 aagtaggtga caagagagtg caaacgaaaa accacgggag gcgaagggaa cgcggtctta 12000 cagaggatga tgccgcgagg aaaggtggac gaacaccctg aaacaggaga gaggaaagcg 12060 agaaccggac aggctcacac caaagtcaga cagaggccac agagcgagaa ggacagggag 12120 gtgcagaagc ggagagaccg gccagaaaag agagagacag gggcggagat aagtgctaca 12180 gaaagtcgag agaagctttc tcgatcctag ctcaggttcg atgtcacctg cctcgcgctg 12240 tgcggcatgg ccacacgcat gctgaaagtc aacgagaagg tcgccaagca gttctacaaa 12300 tcaagcactg tccagacagc tgctgacggg cattccgttt ttccttttgt gggcgtttgt 12360 gtcgctgtct ccgacgttcg gacgtcccgc gactacagcg tctctgactt tccagacgcc 12420 tcgctttctc atctcttctc ccgcttcgct gtcttgtggg ccttttcctc accgcaggtc 12480 aacgcgcgtc tctctcggag cagcgccctc gcgtccaaag ccactggcta ccctttggcc 12540 tacattgcgg cgaagctcgc tctcggtaac gtttgtctcc cttctgtttc gtcgaaactt 12600 ctgagtggct tttccgaact gttcgtccca gagtcgatcc gcatggcccg ctcaaagccc 12660 agcatcccct ttcattgctg ctctccttga tgcttcaagc gtgtctgcac ggccttcctt 12720 ctgttcttaa attcgcggcg gtgatgtgcg tttccgtcta atcttctttg tctcgtcggc 12780 tgagtgaggt ggtgcttcgg tcggttttca tcctcgagaa ctggcagtgt gtgtcgcatg 12840 ttttctctct ccatgtaggc tcgactttgg tggagctcag taactccgtg acaaaagaga 12900 caaccgcctg cttcgagcct tcgctggatt acgtcgtcac caaggtgccg aggtgcgagg 12960 acacaacgca cacagataga agttccatag ggactcccag gacaccagtg gtttcttccc 13020 tcttctcttt gtggcccgac tgctccctcg ttctctcttt cctgcctctc ttcatctctt 13080 cctctgtttc tctcttcgtt gttcctgtcc ttcgccgtct cttccgctgt tcactgttgg 13140 ggtccgttcc agttcggccg tcgcttgcgt gtcaacgtgt gtatggttct ctctcctcaa 13200 cgtcaccacg tcgccagcgt ccttgcccaa aattgtttct gccttctgca ggagctcaac 13260 gccttctgtt agatgcctct ctgacgcatg ctttgcatct ctgcactcga tagagacttg 13320 ccgttttgag gaagaagttt ccagagcgtc tgagagagtg tcctcgcgcg tctctcgacg 13380 tccagcgagg ctcgcgcctc ctggcggtga acagattcgt gttgaatatg tctttctgct 13440 ctcaggtggg atctgcgaaa attcgagtcg tgcgaccccc tgatgggcag cgcgatgaag 13500 agtgtcggcg aggtcatggc cattggacgc accttcgagg agtctctgca aaaggcgctc 13560 aggtaaacca caaagttcca atcatcggca tccgtcgaca aacagttgtc ccagttgaag 13620 ttattgtagc cacatctctc ttctccgcat ttcctctctc ttcctcttct ccctcttgtt 13680 ctccctcttg gtctcccttg tgttctcttt cctgttctct gtttgcgacg tttcttcgac 13740 tgtgtctcgc tgacgtccgt tctggtggcc tgcgttttcg cctctgttct tcagaatggt 13800 ggacgagaag gccggcggct tcgacgagtc ggtctgtcac tttttttcca cggacgagga 13860 ctgcgcgcct tcgctgcccg ggtcagactt caagacgtcc tcctctggag aatgcatgcg 13920 tggcggctgc ggacgcacag actccggcgc cgagcggcag gctgcgctgc tggaggcgga 13980 acttcgccgt ccgtcaccga atcgaatctg ggcgctggcg ctcgccttcc agctcgggtg 14040 gacggtcgac gcgctccacg agaaaacgaa aatcgacaaa tggtttttaa gcaaacttca 14100 aaacatcaac gacatcaagc gacagctcac ccagctcacc ctcgatgacc tcacgcgcgc 14160 agatttcttc tacatcaaga aatacggtaa acgccttcgc gcgctgtcga gacactgggg 14220 catgtggctc gggtgtcttc ggggtggccg tcaaacagtg gggtgtttcc cagtcgcatt 14280 tctcactcgt ttgtacatct ccgaaaacac ggcgacgatg cgcaagccga aggggacaag 14340 agacaagcga tgctccatgt tttcaaagct cctgtctgtt ccccgtctct tgtggcaatc 14400 gtcgaagata cgctaaccgc agactggtgg tcaaatgttt tttttcgttt tgggatccac 14460 tgtggttctc atcttctcgt cgtctcttgt cttcgtctct cgctctcggc ttctcgtctt 14520 ctactcggtc tcccctgctc cgtttcttct cctcgtccgt gtctcatgtt cctcttttct 14580 tctcgccttc ttcgcttcgt ctgtgcaacg accagactgc gacaatccct ccccgttagt 14640 aggataggcc gcaggtttct ctctgtttcc caggattcag cgaccgtcag attgcgcagt 14700 acttgatgaa ttcaccgagc gcggctgcgc tgtcgcagtt cgacgtgcgt cgtcggcgac 14760 tgcacctggg cgtcagaccg tcggtgaagc aaatcgacac tctcgcggcc gagtttcctg 14820 ctcacacgaa ttacctttac ttgacctacc aaggaatcga cgacgacgtc tcgcctctcg 14880 ccgccacgcc gtccgtctcg gcggtcttcg ctggcgcgcg agccgagaag agagaagaag 14940 aaaacgcaga gacatgcaga gacgacgagg acgaaagtct cctccgccgc ctgagcaaaa 15000 gctccagcgc gcggcttaga accggcgaag gcgacgcacc cggaaaacaa tgttttgtgg 15060 ttctaggtag gcgacgaagg caagaaactt tgaggatgga gagacgaaga agcattgaag 15120 ggagagaaat gcaaagacgg gagagagatc gagaaccgga ggagaagaga gaggaatggc 15180 gacagagatc aagggacgag ttggagacga tgcatgaagc aaaggcgagc aaaaaaggcg 15240 attcacggaa gaccagaatc agacgacaag aacatgtctt tgtttatcga cgggcacacc 15300 tctttttctt ttctctcaag gacctgtcgg tgcttgcgca ccaggtactg cgatatatat 15360 atatatatat atatatatac atgaacatcc acagatatgc ttgggtagat acagaagtac 15420 atatatatac atatatatac gactattcat gcatatgcat gtgtatatgc ttttttgcac 15480 ctttttgtgc gttggtattt tttggtgtgt ttcggcaggc tgcggctgct accgcatagg 15540 atccagcgtc gagttcgatt ggtccgctgt ttcgtgtgtc cgtacacttc gctctcttgg 15600 ccaccacgcg attgtggtga gtattcgccg cctctcagtg gtagatcact tcgcaaacgt 15660 ttcggtcctt aggtcaagga atttgcgaca agcctctgcc tcaggttcct cgtgaatagc 15720 ctcagactat ttttaaacaa atgcagcgat gcattaacgc atggggacac tgcatgtgag 15780 atgagccacg gttccgcgaa tatctttatg gatatgtatc aatggataca taaatatata 15840 tatatatata tacatatatt atgtacgcag tggaggccat gtagaaatgg gcatttttac 15900 ctctattcac gaataagagt aggtctgtgc atgacgacga cggacatgaa agtgatgcta 15960 gacagtatat gagcatttaa aaggtaatta ttcataaaag tgtttattga acgttgttcg 16020 tcctgctctt gtcaattcgc attccgtgga acaggtaaac tgcaatcccg agactgtgtc 16080 gacggactac gacgtgagcg atcggctgta tttcgaagac ttgagcttgg aaacagtctt 16140 gaacatctgg taggtttctc acgcgtagct gtccgattgt gggctctccg aatataagcc 16200 gaatcgcggt gaccagcctg gatgtcggcc ttggacgtgt gtctggcccc tcagattccc 16260 cgaacattca gagagagctc acatggcccg taggtttggt gtctctcagt gtgtcatgca 16320 gtgcatcaaa gttcgttctt tgaattcgca catcccgtcg atgtctgtgg gtccgccttg 16380 gatggcgccg cctcgttggt atttgaagtc ccaaataaga ggcacagaaa tcactgtttt 16440 cgctgtgtgg aagacacgtt cttttgtgtg tcccagattt ctctcttctt gtctttcttc 16500 tcacgcttct cttctgtcgt catctgtgcc tcgtgcacgc gtctctgaac tcgtcgtatt 16560 ctcctctctt gctcgtgtct ctttccctcc tgtttgactt tcttttccgt ctcgcttcgc 16620 ttcccttgtt ctcccgtctt gccctcctgc ttcacgcgtt gtctgtcacg tctggctttc 16680 gttggtcgcc tctgttttcc ggagttttct cctcctccac tctcttcttt atctcagaaa 16740 gactttgaag atttaaacag gggtccacct cctattctac actccggaga agaagtcata 16800 ccttcccgcg cggtggtgga ttccattcgc tatcctgtgt ctcctgccta ctagtcaaga 16860 gatgttgcgc gagtgtgtgc ttctcgttcg agggtcctct gtcgtgcgtt tttcgttcgt 16920 ttccagggac attgaagccc cggcgggagt gattatttcc gtgggcggcc agacaccaaa 16980 cacgctgtgc tctgcactgg agaagcaggg cgtgaggatc gtcgggacga gtgtggcggc 17040 gatcgactgc tgcgaggaca gacacaagtt ctcccggctc tgcgacgagc tgaacatcga 17100 ccagccgagg tggaaggagt tcaccgacct tcgcacagcg aaggccttct gccaagaggt 17160 aagcggaaac acatggttca ttcggggcga aacaagagaa aacgggagat ggagatgggg 17220 acgaaaacgg agacgaacga gaagcaatca aatggaaggc aaagcagccg agaaatagag 17280 agacacggag acgcagaaat gtgcgcagag gacagcgaaa cgcagatgaa gcggggggag 17340 acagagcggt cttcaacagc gcgcagtcga gttgaagaag agacgaacga agaacggacg 17400 tcaaaacaca caaggggagc gaaccttgga ggactgataa cagaagacga aaagtcgaat 17460 tggaagatag gaagtcgcag gagagatgac acaacctgtc gaggttccaa aggggtagcg 17520 tgtgcccaag agcaaaagca ttcgccggat gtccttacaa cgtgcttgct ggcgcgacga 17580 caccatcagg ttacctcgaa agtaaatacc gtttctgcat ttttatcgaa gaggtcttct 17640 gtctctgctt ctggcctacg taaaataaaa ggcttgctct gtgaaagccc ctgccggtcc 17700 acatgttcgt accgcacacg cttacagtgg tgtcttgcat gcatttttcg ctggccgttt 17760 ttcttccttt cccttcgcga cggtctgtac gtacgcccga gaccccgttg gtccacaggc 17820 gtccggcgcg gtggtgtctc tggtactccg gcctcgtcga acgtatgttt tctcgcagtt 17880 tgtctggcac gtgtttgaaa ggctgtggat tcgcaagtcg cgttttctgc gttcgttctc 17940 gctcttctct gcaggtcggc tacccagtcc tcgtgcgtcc ttcctacgtt ttgagtggtg 18000 ctgccatgcg agtggtgacc gacgacgagc agctcgacgc cttcctcaaa atcgcagctg 18060 tcgtcagtgg cgaatctccc gtggtcatct ccaagttcgt cgagaacgcc aaggaagtaa 18120 gaaaacgacc tagacaggct cacgacttcc acgcttccac gcatatccct gtatcgtgtt 18180 cgtatctact ttcctgtggg ctacatgtct ccgtgttcct atgcagtgat gtcagagatc 18240 ttcctcgaaa tactctcttc agctgcgtat aggtgtatac ttgcatgata tccatttatc 18300 ttttgcttgc gtatctatgt agatggaaat gcatccgaat gggatatata tatatatata 18360 tatatatatg cgtgtgtttt cttataatta tgtatatata tatataatat cgatgtgtgc 18420 aaacatgtga tctccgctta gatggggaac tcttgagcaa tagtgaggca aacgaaacga 18480 agttgtcaaa atcagcagga accaccggga tgaacctggt gcatgcttgc gtaagcatag 18540 gcgtgcaagc atagtttcac atggtaggca ggagccggca ttgttcggat gtatcgtcct 18600 ctcctcgttc cttccgtgga aactgccttt ttggcttgca ggtggaattt gacagcgtcg 18660 cttgccgggg ggaaatcgta aactttgcaa taagcgagca tgtggagaac gcgggtactc 18720 actctggaga cgcgactttg attctccctg gacagaagct ttacgtggaa acgattcggt 18780 gaggacgcat gaagagtgtg ttgtgacacc cgtccccagt gcgcgacaga gaaaaagaga 18840 cgaactttcc aggaacgcag agagtcttca aagattccgt tcatgagtcg cggctggtgc 18900 atctcgcgcc cattgttttc aaggacgcta cgcgcccgaa cgagtcgtgt tctgtctcag 18960 cgtctccagt tgctgaatgc cgtggtgtca tcccagcaaa cgcaactgtc gctcttgtcg 19020 agagcgcgag aaagagaaca tgcgaaaaga gcgtttgaag ggagtggagg cggcacctgc 19080 atgtaatcga gagaaagaat aatggcttag ttgatgaagg acggtggaga gaaagtgatc 19140 gaacttgagg cgcagtgagg gcgcagagac agcgacaaag acatgtgagg atatccaggc 19200 aagtgtgatg ggagagtcag gtagatattt gccagtggac aatattgcta gaaatggaga 19260 caagatggat gcagggtgaa cggacagtta tcggtcgggg tatacgagaa ataaatgcat 19320 gttgaatgac ttggatagat gagagagaga gagggacgta gtggttcctt ggccttgcgc 19380 cgccttgtcg tgaagggtcg acaccagtca gatggagatt ctgtcgccca catcttcttt 19440 agaagaattg aaaaagctgt tcttgtaagt tgtgaaggca caaatgtttt ttgcgtgcag 19500 tcgcgtgaag aagatctcgc agaaactcgc gcgcgcactc caagtctcag gttcgttttt 19560 ctcatacact atctttcgtt gattgctctt cccctgcttc tcctcaaaaa cctttctttg 19620 cgtcgtgcgt tcgatccggt gtcttctgcc tttctgtcag gtgccaactg tacacggttc 19680 gagtttctgt cttctgagtc gagtgttctt cttcaccatt ttttcgtcgg acttcgtgtc 19740 gctttgtgtt atccgacagt cgatagacct cttttctcca tcacgagaaa gcgacgacgt 19800 tgcctttcct atcgcagctc acccagtgga ggcaaaccgc attggcggat ctgcaattcc 19860 aaaccagagt tcagaggcgc ctgagactgc cggacgttcc ctcgagttcg tgtcagctgc 19920 atgcgttgca tgcgcatgca cagcgccagg gacggggcac ctgcgggtcc gcttgcgaga 19980 gggcgtgctg tgcttttctg cctttcttca ggtccgttca acatccagtt catctgcaaa 20040 cagaacgacg tgaaagtcat tgagtgcaac ttgcgagcgt cgcgtacttt ccccttcatc 20100 agcaaggcct tcaatgtaaa cctcatcgac ctcgcgacaa agtaagaaga ccaagggtat 20160 tccacacgcg cctcaagttc ccttttcaac acactcttcg acacacatct ccgaataaac 20220 ataatctgcg tgcatgtttc tctagacacc gagagatcta cacacgcgca tatgtatata 20280 catatgtata tatatatata tatatactta catatataca tacgtatgtg tgcgtatgat 20340 tccactagag gcaaagctac cggtagggac cgattttgag gtggatttgt ttcgttcttt 20400 ctcttcgttt ccttgtcgtt tcgtctccag ggtgatgatt ggcgcaccgg tcactccgtt 20460 gccgattcac ttgatggacc tttccttcgt ctgcgtgaaa gttccagttt tctctttcgc 20520 gcgtcttcgc ggctgcgacc cggtccttgg cgtggaaatg cggtcgactg gagaagtaag 20580 caggctgctg aagaaggaga cgctattccg ttttcaagtc gggaagcctg gcgtcgtttg 20640 aggcagatct gcattgccgt ctactcggct tggaacgata gacagaggaa gacacaagtg 20700 cgaggaaggg gaaagggagg aaaacagcga aagaggagga aagaagagta cggcacaatg 20760 tgcgagcgaa gcgagaagtg agtgagagtg tttagaagaa caaagtgaga aacgaaaatg 20820 aaacttctgg gtatccttcc ctcaagcgac tgttcgtgga caaacgcagt tttcactcga 20880 gacgtcaacg cgttccgtct ccattgcttg tctcctcgcg accgtgttgc ttttcctttc 20940 acaggttgcg tgcttcggag ccagcaaaca tgaggctttc ctcaaggctc tcatctcggc 21000 tggtgtgccg ctgcctcttg agaagcgaac gattctcatc agcgcaggta cgcaacgttc 21060 tgtaaactaa gcgattcttt ctgttcgctt tctctctgtc gagcgacagc aaccttttcc 21120 tgtctccttc cctccctctc gagacagagc agcttccatg ttccccttag tgttttttaa 21180 cagccgcgtt tctctgaagt cggcgcatgc atctactatt gcagatttcg cttcgtgttc 21240 gtgcgagccg aagaaatgct gcccgtcgcc ctggcccttc gactctctct cctcgtcagt 21300 ttcgctctct ccatttccag ctggcgaaga gtttctatgg acatatgtct gtcggtcgcg 21360 tgtgatgcat gcactgcctc tcggttgtga cattttatcc tcttgtcttt gcaggccctc 21420 tgtggtcgaa gatggaactc gagccgtact tcaaaatcct tttggacctg ggcttcacaa 21480 tctacgcaac ggaaggtaag tggaggcgca ctccatgaat ccctttgcag ttctctcttc 21540 tttttcttct cacactaaca gttggtgttc ctatctatct acctacctct ctatctatgt 21600 ctctctggtt gtctgtctgc ctctcggtcc gtgtatctgt gtatctgtcg gtgcagctct 21660 ctaagccgcg aacggtcgtg cgtatatata tgttcatctg caacacaacg aacgctctgt 21720 atgcacgtgc catgtcgata tgactgtgta cgctggccgt cgttgtctgt gtgcaggtgt 21780 attgcttcgc cgctgcagaa cgtagcatat gtgtctttat tcaacatttt tgaagggata 21840 ttgccttcgg tttctttcag tggcatttag ctaggatttt ttcctttttt ttgaaaggta 21900 gtgaagaacg tgtgttgacg gccagggccg cagcacatgc tgcgatgtct ttcttttgcc 21960 catggtgtgt gtgtgtgtgt cttgtgtggt cgctttggct tttcttcatt ggactgtttt 22020 tcgttttgtg tttcttccat ttttccgttc ttcaagtgca tgcgaaggtt gtcaagcgta 22080 ttctctcgga attggctttc acaaagctct tctgccccgc tcctcgtttg tttccacctt 22140 tcggcttctt tttgttcaac gttcgcatgc tcacacgcat gcacgcctcg atcttttcct 22200 gtcctgacgc agacaagtgc tcttcgtttt actgctgtcc ccgtttccgc tgccccgccg 22260 tgacttctct cgttttgcga gttcacgttt cttctttctt cgtttttctg gattttcttc 22320 ggtgcccagg tacctacaga ttcctcatga acagcgtcgt tcgcgggcag gggacccacc 22380 tgcctgggaa cgcgtcgccg gcgtccgaca gcggccttcg gactcctacg acagccgagt 22440 ccgacgcaga tgcgtgcatt cgcgcgaaat acgcatcgcg cattattcgc gtgagaaagc 22500 cgattgtcgg atcgaatgag tcgcacaacg gaggtcacca gtcacctcac gctctctccc 22560 tcattgaaag tggtaaggcc cggcagtgcg ttttcgggtg gctgtgcaga cggggcatgc 22620 gattttttgc gtttctgagc aacgaggcgc cagcatgtac acacagccca gtggtttatg 22680 tcttgtttgc tttcgtgttg cagtcgcaca tgcatgcact cttatgtgta tgcgcatcta 22740 tcgtgccaag gtccattcac atgcctagtt atgtgcatgc ggaggttgag atgcatactg 22800 aggatggtcg atgtttaaac gattgttgac aggctcagct attgggagcg agcatggttt 22860 ttctctgtga gagttcactg gaccctagac cgtaaacact tgcagagact ggctggaccc 22920 cctcgatcga aaccatgcat gcagcagtca agtcgaccac agacagaaac agacgcacag 22980 cagtgccacg gagatgtagg tgcggcgttc acggaggtag aggtgaacat gtggtttcac 23040 atggcttttt gaattttttc gcaagaagga aagtacgaga acttcctgct atgcacgaat 23100 cgctcatcct ttcttgccga agaacgaaac ggtgtcttgt ttgttcacat agggaaggtc 23160 gaaatggtca tcaatgtgcc tgacagcatg aaccaccgag cgggcacaaa cggctacctg 23220 atgcgtcgca ctgcgaccga ctgcggaggt gcgttttgcc tcagtgggcg caacagacga 23280 accaaagaaa cgaaagaaaa gacagaaaaa aatggtggaa ctcgtgctct agcaaaacgg 23340 actacccgac ggaactgcaa agcgtctgtc tggtccgagg gcgtcttgcc gttcccgact 23400 gggcgttcga aaaaagcaag tcttctccat ttcatgtttt ggcggcccgc gcaagcaaca 23460 gtaatcttca ctggcttggc ccaccgactc tcacgacctc agttcagtat gcgggcgcgg 23520 ggaatcaagt gcgaaatact cgttttctac ataattatat atatatatat atatgtatat 23580 acgcgtacat agatataaat acggacatgt agacagatgt atgcatatgc atatatagtt 23640 acaaacgtgt atagatttag acagattcgt aatattttgt gtatgtttcg atcaatacat 23700 taacgtttcg cttgcaatca gatgcgtcga tggcctcaac agtcgacaga gcatggggta 23760 cgctgttttc tggggtcggg aacgtttcag aaatctcgtc agagagagcg ggcttctccg 23820 cgccattggc gtttgcgtgt ctgcaatatg ttgatcggcg tttacgtcgt tttcttgttt 23880 ttctcttcgc agttcccctc ctgacaaacg tcaaagtggc aagcatgttc gtcgaggccc 23940 tcaacaagaa agaagcgaaa gaagctcagg gtcgctcctt ctgggacatt cgcagctggg 24000 atgaatactg gcctcaaaaa taa 24023 2 5064 DNA Toxoplasma gondii 2 atgcctcaca gtggagggcg gagagctgtt gctcccattt accctctcga tctggcagga 60 cgtctgagac ctgcaatgct ggtgttagcc gatgggactg agtttctcgg atactccttc 120 ggctacccag gcagtgtggg aggcgaggtc gttttcaaca ctggtatggt cggctacccc 180 gagtctctga cggatccttc gtacgagggg cagatcctcg ttctcacata ccctctcatc 240 ggcaactatg gcgttccctc ttcggaaaaa gatgagcatg gcctgccgaa atactttgag 300 ggcgaccgca tttacgttcg cgctctcgtt gtggcggact acgacaacgc agccgtgacg 360 gcacactttc gtgcagagaa cagcctcagt gcttggatga acactcacaa agtcccggcg 420 attgcaggag tcgacacgcg agcgttgacc aagcacctgc gcgaggtcgg ctgcatgctg 480 ggcaagatcg tcgtcctgag cgaagaagaa gagcgtcgat ccggcttgtc gctctcggct 540 ctcgccgcgc ttccctcagc gactgcagca gagcaacgag gagagaacga cgcgacggtg 600 acgcccgaca aagcagaggc ccgcctaaga gtggagaggc gacaagcagc gctcacgatg 660 tgggaggagg cgatccgcaa caaggcgaag aacctgccat gggaagaccc caacaaagac 720 aacctcgtcg ccctcgtttc gcgaaaagaa gtgcgcgtgt acaaatctac tgtcgtggat 780 ccgaatctcc gcgacgtcct catcctctgc gtggactgcg ggatgaaata caacatctac 840 cgccagcttc tccatagcaa attcgagcac tgcaacatca ttctcaaggt ggtgccgtgg 900 gatttcgact ttggcaacga cgaatttgac gggctcttca tcagcaacgg tccaggcgac 960 cctgagagat gcgaaaaaac agttgctaac attcgacgcg tcatggagcg aaagatcccc 1020 atcttcggca tctgcctagg aaaccaactt cttgccctgg ctgccggcgc gagaacgtac 1080 aaaatgaaat acggaaacag aggaatgaat cagccggtga tcgacttgcg aacgtcgaga 1140 tgctacatca caccccagaa ccatggcttt gccgtcgacg agagcacgct gcctcgagat 1200 ttcctgccgc tctttgtaaa tgcaaacgac cgttcgaacg aaggcatcat ccatcgcacg 1260 ctgccttttt tctctgcaca gttccaccca gaggcgtcag gtggtccgac agacacgttt 1320 tacttatttg gcgacttcat cgcctcgatt atgaaggcgc agacgctgaa gcaggtccac 1380 acgactccgt tctcctttcc gcagaagttc cagaaagttc tgcttctcgg gagcggaggc 1440 ctgagcatcg gccaagccgg ggagttcgac tacagcggct ctcaggcgat aaaggcgctg 1500 aaagagcaga acatctttgt cgtcgtggtg aaccctaaca tcgccacggt gcagaccagc 1560 cagcacatgg ccgaccgggt gtacttcctg cccgtcacgg atgagttcgt gacgaaagtc 1620 atcgaaaagg aaatgcccga cggcattctc tgcacattcg gaggccagac ggccctcaac 1680 tgcgctgtga aactccacga acaaggcgtc ctggcaaaat tcggctgcaa aatcctcggc 1740 agtccaatcg aagcgatcat tgcgactgag gatcgaaagg tgtttgcggc gaagctggaa 1800 gaaatcggag aaaaagtggc ggagagcgcg gccgcgacaa acacggaaga agctgtgcaa 1860 gcggcgaagg ccattggcta ccccgtcctc attcgcgccg ccttcgcact cggtgggctc 1920 ggatctgggt tcgccgagga cgaggagacc gtccgacgca tttgcaagga agccttctcc 1980 cattcttctc aggttttcgt ggacaaaagc ctgaagggct ggaaggaggt ggagtacgaa 2040 gtcgttcgcg actgcaagaa caactgcatc accgtctgca acatggagaa cttggatccc 2100 ctcggcatcc acacgggaga ttcgattgtc gttgctcctt cgcagacgct gtctaacgag 2160 gactactacc gcctgagaga taccgcgctg aaggtgattc gtcacttcgg catcgtcggc 2220 gaatgcaaca tccaatacgc gctcgaccct aactcggaga aatactacat cgtcgaagtc 2280 aacgcgcgtc tctctcggag cagcgccctc gcgtccaaag ccactggcta ccctttggcc 2340 tacattgcgg cgaagctcgc tctcggctcg actttggtgg agctcagtaa ctccgtgaca 2400 aaagagacaa ccgcctgctt cgagccttcg ctggattacg tcgtcaccaa ggtgccgagg 2460 tgggatctgc gaaaattcga gtcgtgcgac cccctgatgg gcagcgcgat gaagagtgtc 2520 ggcgaggtca tggccattgg acgcaccttc gaggagtctc tgcaaaaggc gctcagaatg 2580 gtggacgaga aggccggcgg cttcgacgag tcggtctgtc actttttttc cacggacgag 2640 gactgcgcgc cttcgctgcc cgggtcagac ttcaagacgt cctcctctgg agaatgcatg 2700 cgtggcggct gcggacgcac agactccggc gccgagcggc aggctgcgct gctggaggcg 2760 gaacttcgcc gtccgtcacc gaatcgaatc tgggcgctgg cgctcgcctt ccagctcggg 2820 tggacggtcg acgcgctcca cgagaaaacg aaaatcgaca aatggttttt aagcaaactt 2880 caaaacatca acgacatcaa gcgacagctc acccagctca ccctcgatga cctcacgcgc 2940 gcagatttct tctacatcaa gaaatacgga ttcagcgacc gtcagattgc gcagtacttg 3000 atgaattcac cgagcgcggc tgcgctgtcg cagttcgacg tgcgtcgtcg gcgactgcac 3060 ctgggcgtca gaccgtcggt gaagcaaatc gacactctcg cggccgagtt tcctgctcac 3120 acgaattacc tttacttgac ctaccaagga atcgacgacg acgtctcgcc tctcgccgcc 3180 acgccgtccg tctcggcggt cttcgctggc gcgcgagccg agaagagaga agaagaaaac 3240 gcagagacat gcagagacga cgaggacgaa agtctcctcc gccgcctgag caaaagctcc 3300 agcgcgcggc ttagaaccgg cgaaggcgac gcacccggaa aacaatgttt tgtggttcta 3360 ggctgcggct gctaccgcat aggatccagc gtcgagttcg attggtccgc tgtttcgtgt 3420 gtccgtacac ttcgctctct tggccaccac gcgattgtgg taaactgcaa tcccgagact 3480 gtgtcgacgg actacgacgt gagcgatcgg ctgtatttcg aagacttgag cttggaaaca 3540 gtcttgaaca tctgggacat tgaagccccg gcgggagtga ttatttccgt gggcggccag 3600 acaccaaaca cgctgtgctc tgcactggag aagcagggcg tgaggatcgt cgggacgagt 3660 gtggcggcga tcgactgctg cgaggacaga cacaagttct cccggctctg cgacgagctg 3720 aacatcgacc agccgaggtg gaaggagttc accgaccttc gcacagcgaa ggccttctgc 3780 caagaggtcg gctacccagt cctcgtgcgt ccttcctacg ttttgagtgg tgctgccatg 3840 cgagtggtga ccgacgacga gcagctcgac gccttcctca aaatcgcagc tgtcgtcagt 3900 ggcgaatctc ccgtggtcat ctccaagttc gtcgagaacg ccaaggaagt ggaatttgac 3960 agcgtcgctt gccgggggga aatcgtaaac tttgcaataa gcgagcatgt ggagaacgcg 4020 ggtactcact ctggagacgc gactttgatt ctccctggac agaagcttta cgtggaaacg 4080 attcgtcgcg tgaagaagat ctcgcagaaa ctcgcgcgcg cactccaagt ctcaggtccg 4140 ttcaacatcc agttcatctg caaacagaac gacgtgaaag tcattgagtg caacttgcga 4200 gcgtcgcgta ctttcccctt catcagcaag gccttcaatg taaacctcat cgacctcgcg 4260 acaaaggtga tgattggcgc accggtcact ccgttgccga ttcacttgat ggacctttcc 4320 ttcgtctgcg tgaaagttcc agttttctct ttcgcgcgtc ttcgcggctg cgacccggtc 4380 cttggcgtgg aaatgcggtc gactggagaa gttgcgtgct tcggagccag caaacatgag 4440 gctttcctca aggctctcat ctcggctggt gtgccgctgc ctcttgagaa gcgaacgatt 4500 ctcatcagcg caggccctct gtggtcgaag atggaactcg agccgtactt caaaatcctt 4560 ttggacctgg gcttcacaat ctacgcaacg gaaggtacct acagattcct catgaacagc 4620 gtcgttcgcg ggcaggggac ccacctgcct gggaacgcgt cgccggcgtc cgacagcggc 4680 cttcggactc ctacgacagc cgagtccgac gcagatgcgt gcattcgcgc gaaatacgca 4740 tcgcgcatta ttcgcgtgag aaagccgatt gtcggatcga atgagtcgca caacggaggt 4800 caccagtcac ctcacgctct ctccctcatt gaaagtggga aggtcgaaat ggtcatcaat 4860 gtgcctgaca gcatgaacca ccgagcgggc acaaacggct acctgatgcg tcgcactgcg 4920 accgactgcg gagttcccct cctgacaaac gtcaaagtgg caagcatgtt cgtcgaggcc 4980 ctcaacaaga aagaagcgaa agaagctcag ggtcgctcct tctgggacat tcgcagctgg 5040 gatgaatact ggcctcaaaa ataa 5064 3 1687 PRT Toxoplasma gondii 3 Met Pro His Ser Gly Gly Arg Arg Ala Val Ala Pro Ile Tyr Pro Leu 1 5 10 15 Asp Leu Ala Gly Arg Leu Arg Pro Ala Met Leu Val Leu Ala Asp Gly 20 25 30 Thr Glu Phe Leu Gly Tyr Ser Phe Gly Tyr Pro Gly Ser Val Gly Gly 35 40 45 Glu Val Val Phe Asn Thr Gly Met Val Gly Tyr Pro Glu Ser Leu Thr 50 55 60 Asp Pro Ser Tyr Glu Gly Gln Ile Leu Val Leu Thr Tyr Pro Leu Ile 65 70 75 80 Gly Asn Tyr Gly Val Pro Ser Ser Glu Lys Asp Glu His Gly Leu Pro 85 90 95 Lys Tyr Phe Glu Gly Asp Arg Ile Tyr Val Arg Ala Leu Val Val Ala 100 105 110 Asp Tyr Asp Asn Ala Ala Val Thr Ala His Phe Arg Ala Glu Asn Ser 115 120 125 Leu Ser Ala Trp Met Asn Thr His Lys Val Pro Ala Ile Ala Gly Val 130 135 140 Asp Thr Arg Ala Leu Thr Lys His Leu Arg Glu Val Gly Cys Met Leu 145 150 155 160 Gly Lys Ile Val Val Leu Ser Glu Glu Glu Glu Arg Arg Ser Gly Leu 165 170 175 Ser Leu Ser Ala Leu Ala Ala Leu Pro Ser Ala Thr Ala Ala Glu Gln 180 185 190 Arg Gly Glu Asn Asp Ala Thr Val Thr Pro Asp Lys Ala Glu Ala Arg 195 200 205 Leu Arg Val Glu Arg Arg Gln Ala Ala Leu Thr Met Trp Glu Glu Ala 210 215 220 Ile Arg Asn Lys Ala Lys Asn Leu Pro Trp Glu Asp Pro Asn Lys Asp 225 230 235 240 Asn Leu Val Ala Leu Val Ser Arg Lys Glu Val Arg Val Tyr Lys Ser 245 250 255 Thr Val Val Asp Pro Asn Leu Arg Asp Val Leu Ile Leu Cys Val Asp 260 265 270 Cys Gly Met Lys Tyr Asn Ile Tyr Arg Gln Leu Leu His Ser Lys Phe 275 280 285 Glu His Cys Asn Ile Ile Leu Lys Val Val Pro Trp Asp Phe Asp Phe 290 295 300 Gly Asn Asp Glu Phe Asp Gly Leu Phe Ile Ser Asn Gly Pro Gly Asp 305 310 315 320 Pro Glu Arg Cys Glu Lys Thr Val Ala Asn Ile Arg Arg Val Met Glu 325 330 335 Arg Lys Ile Pro Ile Phe Gly Ile Cys Leu Gly Asn Gln Leu Leu Ala 340 345 350 Leu Ala Ala Gly Ala Arg Thr Tyr Lys Met Lys Tyr Gly Asn Arg Gly 355 360 365 Met Asn Gln Pro Val Ile Asp Leu Arg Thr Ser Arg Cys Tyr Ile Thr 370 375 380 Pro Gln Asn His Gly Phe Ala Val Asp Glu Ser Thr Leu Pro Arg Asp 385 390 395 400 Phe Leu Pro Leu Phe Val Asn Ala Asn Asp Arg Ser Asn Glu Gly Ile 405 410 415 Ile His Arg Thr Leu Pro Phe Phe Ser Ala Gln Phe His Pro Glu Ala 420 425 430 Ser Gly Gly Pro Thr Asp Thr Phe Tyr Leu Phe Gly Asp Phe Ile Ala 435 440 445 Ser Ile Met Lys Ala Gln Thr Leu Lys Gln Val His Thr Thr Pro Phe 450 455 460 Ser Phe Pro Gln Lys Phe Gln Lys Val Leu Leu Leu Gly Ser Gly Gly 465 470 475 480 Leu Ser Ile Gly Gln Ala Gly Glu Phe Asp Tyr Ser Gly Ser Gln Ala 485 490 495 Ile Lys Ala Leu Lys Glu Gln Asn Ile Phe Val Val Val Val Asn Pro 500 505 510 Asn Ile Ala Thr Val Gln Thr Ser Gln His Met Ala Asp Arg Val Tyr 515 520 525 Phe Leu Pro Val Thr Asp Glu Phe Val Thr Lys Val Ile Glu Lys Glu 530 535 540 Met Pro Asp Gly Ile Leu Cys Thr Phe Gly Gly Gln Thr Ala Leu Asn 545 550 555 560 Cys Ala Val Lys Leu His Glu Gln Gly Val Leu Ala Lys Phe Gly Cys 565 570 575 Lys Ile Leu Gly Ser Pro Ile Glu Ala Ile Ile Ala Thr Glu Asp Arg 580 585 590 Lys Val Phe Ala Ala Lys Leu Glu Glu Ile Gly Glu Lys Val Ala Glu 595 600 605 Ser Ala Ala Ala Thr Asn Thr Glu Glu Ala Val Gln Ala Ala Lys Ala 610 615 620 Ile Gly Tyr Pro Val Leu Ile Arg Ala Ala Phe Ala Leu Gly Gly Leu 625 630 635 640 Gly Ser Gly Phe Ala Glu Asp Glu Glu Thr Val Arg Arg Ile Cys Lys 645 650 655 Glu Ala Phe Ser His Ser Ser Gln Val Phe Val Asp Lys Ser Leu Lys 660 665 670 Gly Trp Lys Glu Val Glu Tyr Glu Val Val Arg Asp Cys Lys Asn Asn 675 680 685 Cys Ile Thr Val Cys Asn Met Glu Asn Leu Asp Pro Leu Gly Ile His 690 695 700 Thr Gly Asp Ser Ile Val Val Ala Pro Ser Gln Thr Leu Ser Asn Glu 705 710 715 720 Asp Tyr Tyr Arg Leu Arg Asp Thr Ala Leu Lys Val Ile Arg His Phe 725 730 735 Gly Ile Val Gly Glu Cys Asn Ile Gln Tyr Ala Leu Asp Pro Asn Ser 740 745 750 Glu Lys Tyr Tyr Ile Val Glu Val Asn Ala Arg Leu Ser Arg Ser Ser 755 760 765 Ala Leu Ala Ser Lys Ala Thr Gly Tyr Pro Leu Ala Tyr Ile Ala Ala 770 775 780 Lys Leu Ala Leu Gly Ser Thr Leu Val Glu Leu Ser Asn Ser Val Thr 785 790 795 800 Lys Glu Thr Thr Ala Cys Phe Glu Pro Ser Leu Asp Tyr Val Val Thr 805 810 815 Lys Val Pro Arg Trp Asp Leu Arg Lys Phe Glu Ser Cys Asp Pro Leu 820 825 830 Met Gly Ser Ala Met Lys Ser Val Gly Glu Val Met Ala Ile Gly Arg 835 840 845 Thr Phe Glu Glu Ser Leu Gln Lys Ala Leu Arg Met Val Asp Glu Lys 850 855 860 Ala Gly Gly Phe Asp Glu Ser Val Cys His Phe Phe Ser Thr Asp Glu 865 870 875 880 Asp Cys Ala Pro Ser Leu Pro Gly Ser Asp Phe Lys Thr Ser Ser Ser 885 890 895 Gly Glu Cys Met Arg Gly Gly Cys Gly Arg Thr Asp Ser Gly Ala Glu 900 905 910 Arg Gln Ala Ala Leu Leu Glu Ala Glu Leu Arg Arg Pro Ser Pro Asn 915 920 925 Arg Ile Trp Ala Leu Ala Leu Ala Phe Gln Leu Gly Trp Thr Val Asp 930 935 940 Ala Leu His Glu Lys Thr Lys Ile Asp Lys Trp Phe Leu Ser Lys Leu 945 950 955 960 Gln Asn Ile Asn Asp Ile Lys Arg Gln Leu Thr Gln Leu Thr Leu Asp 965 970 975 Asp Leu Thr Arg Ala Asp Phe Phe Tyr Ile Lys Lys Tyr Gly Phe Ser 980 985 990 Asp Arg Gln Ile Ala Gln Tyr Leu Met Asn Ser Pro Ser Ala Ala Ala 995 1000 1005 Leu Ser Gln Phe Asp Val Arg Arg Arg Arg Leu His Leu Gly Val 1010 1015 1020 Arg Pro Ser Val Lys Gln Ile Asp Thr Leu Ala Ala Glu Phe Pro 1025 1030 1035 Ala His Thr Asn Tyr Leu Tyr Leu Thr Tyr Gln Gly Ile Asp Asp 1040 1045 1050 Asp Val Ser Pro Leu Ala Ala Thr Pro Ser Val Ser Ala Val Phe 1055 1060 1065 Ala Gly Ala Arg Ala Glu Lys Arg Glu Glu Glu Asn Ala Glu Thr 1070 1075 1080 Cys Arg Asp Asp Glu Asp Glu Ser Leu Leu Arg Arg Leu Ser Lys 1085 1090 1095 Ser Ser Ser Ala Arg Leu Arg Thr Gly Glu Gly Asp Ala Pro Gly 1100 1105 1110 Lys Gln Cys Phe Val Val Leu Gly Cys Gly Cys Tyr Arg Ile Gly 1115 1120 1125 Ser Ser Val Glu Phe Asp Trp Ser Ala Val Ser Cys Val Arg Thr 1130 1135 1140 Leu Arg Ser Leu Gly His His Ala Ile Val Val Asn Cys Asn Pro 1145 1150 1155 Glu Thr Val Ser Thr Asp Tyr Asp Val Ser Asp Arg Leu Tyr Phe 1160 1165 1170 Glu Asp Leu Ser Leu Glu Thr Val Leu Asn Ile Trp Asp Ile Glu 1175 1180 1185 Ala Pro Ala Gly Val Ile Ile Ser Val Gly Gly Gln Thr Pro Asn 1190 1195 1200 Thr Leu Cys Ser Ala Leu Glu Lys Gln Gly Val Arg Ile Val Gly 1205 1210 1215 Thr Ser Val Ala Ala Ile Asp Cys Cys Glu Asp Arg His Lys Phe 1220 1225 1230 Ser Arg Leu Cys Asp Glu Leu Asn Ile Asp Gln Pro Arg Trp Lys 1235 1240 1245 Glu Phe Thr Asp Leu Arg Thr Ala Lys Ala Phe Cys Gln Glu Val 1250 1255 1260 Gly Tyr Pro Val Leu Val Arg Pro Ser Tyr Val Leu Ser Gly Ala 1265 1270 1275 Ala Met Arg Val Val Thr Asp Asp Glu Gln Leu Asp Ala Phe Leu 1280 1285 1290 Lys Ile Ala Ala Val Val Ser Gly Glu Ser Pro Val Val Ile Ser 1295 1300 1305 Lys Phe Val Glu Asn Ala Lys Glu Val Glu Phe Asp Ser Val Ala 1310 1315 1320 Cys Arg Gly Glu Ile Val Asn Phe Ala Ile Ser Glu His Val Glu 1325 1330 1335 Asn Ala Gly Thr His Ser Gly Asp Ala Thr Leu Ile Leu Pro Gly 1340 1345 1350 Gln Lys Leu Tyr Val Glu Thr Ile Arg Arg Val Lys Lys Ile Ser 1355 1360 1365 Gln Lys Leu Ala Arg Ala Leu Gln Val Ser Gly Pro Phe Asn Ile 1370 1375 1380 Gln Phe Ile Cys Lys Gln Asn Asp Val Lys Val Ile Glu Cys Asn 1385 1390 1395 Leu Arg Ala Ser Arg Thr Phe Pro Phe Ile Ser Lys Ala Phe Asn 1400 1405 1410 Val Asn Leu Ile Asp Leu Ala Thr Lys Val Met Ile Gly Ala Pro 1415 1420 1425 Val Thr Pro Leu Pro Ile His Leu Met Asp Leu Ser Phe Val Cys 1430 1435 1440 Val Lys Val Pro Val Phe Ser Phe Ala Arg Leu Arg Gly Cys Asp 1445 1450 1455 Pro Val Leu Gly Val Glu Met Arg Ser Thr Gly Glu Val Ala Cys 1460 1465 1470 Phe Gly Ala Ser Lys His Glu Ala Phe Leu Lys Ala Leu Ile Ser 1475 1480 1485 Ala Gly Val Pro Leu Pro Leu Glu Lys Arg Thr Ile Leu Ile Ser 1490 1495 1500 Ala Gly Pro Leu Trp Ser Lys Met Glu Leu Glu Pro Tyr Phe Lys 1505 1510 1515 Ile Leu Leu Asp Leu Gly Phe Thr Ile Tyr Ala Thr Glu Gly Thr 1520 1525 1530 Tyr Arg Phe Leu Met Asn Ser Val Val Arg Gly Gln Gly Thr His 1535 1540 1545 Leu Pro Gly Asn Ala Ser Pro Ala Ser Asp Ser Gly Leu Arg Thr 1550 1555 1560 Pro Thr Thr Ala Glu Ser Asp Ala Asp Ala Cys Ile Arg Ala Lys 1565 1570 1575 Tyr Ala Ser Arg Ile Ile Arg Val Arg Lys Pro Ile Val Gly Ser 1580 1585 1590 Asn Glu Ser His Asn Gly Gly His Gln Ser Pro His Ala Leu Ser 1595 1600 1605 Leu Ile Glu Ser Gly Lys Val Glu Met Val Ile Asn Val Pro Asp 1610 1615 1620 Ser Met Asn His Arg Ala Gly Thr Asn Gly Tyr Leu Met Arg Arg 1625 1630 1635 Thr Ala Thr Asp Cys Gly Val Pro Leu Leu Thr Asn Val Lys Val 1640 1645 1650 Ala Ser Met Phe Val Glu Ala Leu Asn Lys Lys Glu Ala Lys Glu 1655 1660 1665 Ala Gln Gly Arg Ser Phe Trp Asp Ile Arg Ser Trp Asp Glu Tyr 1670 1675 1680 Trp Pro Gln Lys 1685 4 24 DNA Artificial Sequence Degenerate Oligonucleotide Primer. 4 ccnytnggna thcayacngg ngay 24 5 30 DNA Artificial Sequence Degenerate Oligonucleotide Primer. 5 ytcytcmaan gtyctnccka tngacatnac 30 6 10 PRT Artificial Sequence Conserved amino acid sequence of CPSII domain. 6 Pro Leu Gly Ile His Thr Gly Asp Ser Ile 1 5 10 7 12 PRT Artificial Sequence Conserved amino acid sequence of CPSII domain. 7 Gly Glu Val Met Ser Ile Gly Arg Thr Phe Glu Glu 1 5 10 8 33 DNA Artificial Sequence Synthetic Oligonucleotide Primer. 8 gggagatcta tggcttcgta ccccggccat caa 33 9 32 DNA Artificial Sequence Synthetic Oligonucleotide Primer. 9 ggggatcctc agttagcctc ccccatctcc cg 32 

What is claimed is:
 1. An isolated nucleic acid sequence encoding carbamoyl phosphate synthase of T. gondii.
 2. The nucleic acid sequence of claim 1 comprising SEQ ID NO:1 or SEQ ID NO:2.
 3. A pyrimidine auxotroph mutant of an apicomplexan wherein one of six enzymes of the de novo pyrimidine biosynthesis pathway of apicomplexans is mutated.
 4. The pyrimidine auxotroph mutant of claim 3 wherein the apicomplexan is T. gondii.
 5. A method for protecting an animal against infection by an apicomplexan comprising administering to an animal a pyrimidine auxotroph mutant of claim
 3. 6. The method of claim 5 wherein the apicomplexan is T. gondii.
 7. A method for screening for inhibitors of pyrimidine salvage enzymes in apicomplexans comprising: contacting a pyrimidine auxotroph mutant of claim 3 with a compound suspected of being an inhibitor of a pyrimidine salvage enzyme; and determining growth of the pyrimidine auxotroph mutant in the presence of the compound, wherein inhibition of growth of the mutant is indicative of the compound being an inhibitor of a pyrimidine salvage enzyme.
 8. A vaccine for protection against infection by an apicomplexan comprising the pyrimidine auxotroph mutant of claim 3 and a pharmaceutically acceptable carrier or diluent. 